I just took my pre-boil sample and it came out to 1.032, my target is 1.040.

Taking 32 x 15 (gallons pre boil) = 480

I boil off around 1.8 gallons an hour (electric setup).

I estimate that I don't pick up around .75 gallons from the bottom of the kettle. Combine that with hop losses of .18 according to BF, and .25 in misc losses.

But those are besides the fact. If you take 480 / 40 (my target) = 12. However, 12 gallons is the FINISHED product going into the fermenter. By my math I will have more like 13 gallons left in the kettle at the end of the boil leaving me short on my gravity number ~ 36.9.

Do I have something calibrated wrong in the software? It seems to me more than a coincidence that my gravity number comes out to exactly 12 gallons and that is what I put in the system as going into the fermenter.