Brian - It's me again. If I have not steered you wrong yet, then you can proceed. Or you can wait for somebody else to chime in here (Hint)

Your BIABacus file for the stout looks good but I have a few questions. In Section C there are EBC and SRM values for some, but not all grains. You can refer to Section Y where you can enter specific values if you have them and leave those fields blank in Section C - the BIABacus makes some assumptions and takes care of it for you. To fill in some and leave others out can make it so that the sums are not meaningful. Either way, SRM or EDC values are somewhat subjective. They can be quantified but I don't want Tyndall beams, spectrophotometers and APHA color charts in my life.
A hopsock will retain particles from the hops and allow them to be lifted clear of the wort, leaving much less matter contributing to trub. That means you get more wort into your fermenter (VIF) and less KFL. You have specified a desired VIF in Section B that generates both the grain weights and the total water needed (TWN). If you leave all the hops-related matter in the kettle (no hopsock), you will invariably leave wort behind with it. Hence more water and more grains would be required to get the same Specific Gravity and volume that you want. The amount of wort retained in the pulled hopsock is much less than the KFL amount of wort that would be left in the kettle with the increased trub if there was no hopsock employed. [if there are those who transfer the entire kettle contents to a primary fermenter, the trub and wort balances/costs will come later]
In Section D I would recommend entering Kent Goldings in the blank field for time zero addition simply because it makes it unambiguous.

Good job Brian.

Brian, you are doing fine. Keep asking questions, too.

I don't understand what the difference between TWN and SWN is

TWN is what it indicates - the absolute Total Water Needed as an ingredient for the recipe. SWN can be different due to the fact that one might be holding water back in Section W, BUT if Section W is blank, SWN will be greater than TWN because water expands as it is heated. I am not sure how to answer your question if you are steeping grains in some of the TWN outside of the mash in the kettle. I don't steep grains separately.

I expect that Mash Volume is water plus malt, and thus VIB is liquor remaining once the bag of malt has been removed.

You are correct - the mash volume is how full the kettle will be for the time of mashing. VIB is to be measured at the start of the boil. The bag was pulled well before this at a lower temperature. This can be a little fuzzy because foaming sometimes occurs at the same time as boiling starts and it makes measuring difficult (especially if you are brewing solo). Move the spreadsheet on your screen to see Sections U and V over on the right. Section U is the height of the liquid in your kettle according to the dimensions you entered in Section B. Section V is the headspace, or the empty part of your kettle from the top of the liquid to the rim. I prefer to measure without sticking anything other than a thermometer into the liquid, so a metal tape measure works well to measure the headspace*. VIB can also vary according to the spent grain holding different amounts of liquid depending on the recipe or the brew day, or squeezing.

Is VFO higher than VAW because of crud left in the kettle? If so, why is there a further loss (KFL) separate from the VFO VAW loss?

VFO / VAW difference is really due to the volume difference related to temperature. The difference between VAW and VIF is KFL. The KFL in my experience is variable because the amount of trub and how much of it gets transferred from Kettle to Fermenter is both recipe dependent and related to my transfer technique on that day. I am not very picky about keeping all the trub out of my primary fermenter. This also entails having accurate marks on fermenters, or measuring headspace prior to fastening the lid down.

Finally, how do I measure the volumes VIB and VAW accurately? My kettle does not have volume marking on it.

I'll have to look for a link on how to scribe long-lasting markings on a kettle wall, it was a long time ago that I saw it. I chose to not do that because of resulting scratches or bumps in my kettle wall. However, you can mark the outside with a sharpie. It is not super accurate, but it may help. Sections U and V again (see above).

Keep asking questions!

*Technically, the headspace measured also depends on the temperature of the liquid and the expansion associated with it when hot. How precise does one need to be? TWN @ STP?

This was something I wrote a long time ago. It may help with understanding terminology & why we do it?

It is buried in a thread on the site somewehere, showing how it evolved. Give it a quick look and see if it helps.

Cheers

Another Brian - Congratulations!

Two thermometers - one cannot be sure which one is correct. Calibration suggestions are welcome, I hope others can help. Boiling water = 212 deg F or 100 deg C at sea level, lower T at higher elevations; methanol and water do not give an azeotrope, so windshield washer fluid with MeOH as the anti-freeze component will show first sign of boiling (stalled temperature rise on your thermometer) at 60 deg C (140 deg F) Keep your volume down, don’t breathe the fumes, etc. You will have to cope with your thermometers somehow.

Irish moss at 15 min is OK but some say that it (or whirlfloc tab fraction) at 5 min. Is just as good or better.

Adding water will change the Specific gravity. That will be OK as long as you know, measure the impact, and it is in keeping with the style you are making.

Do not worry so much about getting trub in your primary fermenter. It doesn’t’ hurt. Your aeration method will work. Kudos to you for good pouring technique. Your pitching temp could be lower (below 68 deg F, 20 deg C) but the yeast will survive and go to work. Keep track of temp on at least a daily basis. Racking to a secondary fermenter after three days is a good thing if you worry about trub. It does more than get the beer off that trub. It re-aerated the liquor; some say that’s bad but if your yeast is still reproducing, it is not entirely bad.

As for when to bottle - be patient!
With a new hydrometer (ironic how gravity destroyed the instrument used to measure ‘gravity’) take as small a sample from your secondary fermenter as required to float your hydrometer. Write down the number, wait three days and repeat. If those two numbers are the same, then proceed to bottling. Do not return any samples to the batch, you can drink them. If the beer is too cloudy for you, read up on cold crashing. When bottling, you will leave behind some more crud at the bottom of the secondary fermenter and still have sediment in your bottled beer. It’s good, just don’t dump the entire bottle into a glass served to a guest.

After bottling - be patient!
Mind the storage temperature.
At two weeks you will want to have a taste. Go ahead and waste a bottle to learn that you should have waited out the third week.

Congratulations - you will get beer.