That should be fine Phillip however your plan to take a second reading is sensible (I'll give you another tip on this at the end of this post) because:

1. Hydrometers can be inaccurate (as can refractometers)
2. Samples can sometimes not reflect the gravity of the fermenter
3. Final gravity estimates from software are ball-park figures (yeast attenuation is affected by lots of factors)

One way to save taking several samples is to just take one after your fermentation activity settles down (say after 4 days). Then leave your hydrometer in your hydrometer jar and cover the whole lot with something to protect it from bugs. Leave the jar beside your fermenter and then, you'll be able to see the gravity drop as the brew progresses without having to take additional samples.


PP

"One way to save taking several samples is to just take one after your fermentation activity settles down (say after 4 days). Then leave your hydrometer in your hydrometer jar and cover the whole lot with something to protect it from bugs. Leave the jar beside your fermenter and then, you'll be able to see the gravity drop as the brew progresses without having to take additional samples."

Whoa - PP, what a great idea!

I did the hydro in the test jar for a lager of mine. It worked perfectly, just as PP said it would do. The only caveat is to start with a full test jar and then add top up water because of evaporation, if needed along the way.


11-JUN; Pitched, hydro jar in fermenter chamber to monitor progress using a Brix Saccharometer 0 - 8.5 range

In this first photo (from right to left)
This photo taken on 20-JUN; on day 9 (notice evaporation taken place in 9 days)

22-JUN; ...more evaporation on day 11

23 JUN; day 12 topped up with water to the brim to make up for evaporation; measures about 3.74 °Brix
03-JUL; measures 2.5 ish °Brix plus the 0.4 temperature offset to add equals 2.9 °Brix

Do wonder if hydrometer could be pulled and small jar covered to stop evaporation. It seems like topping off will make reading wrong?.?.? Yes I understand you add water back but that seems like it could cause accuracy issues.?..?. If carefully mark initial fluid level it “should” be right. Seems like pulling the hydrometer and covering the jar with kitchen plastic wrap would take care of the evaporation issue but you would have to put hydrometer back in the jar each time you want to check.

I just put a plastic bag loosely over the lot but I've wanted something a bit more elegant...
Next time I might cut the finger off a disposable glove. Only issue with that would be that it might blow off but a pin prick in it would fix that though