I'm an experienced brewer, but a BS3 noob, having a hard time understanding BS3's gravity calculation, as it seems to consistently estimate a higher post-boil gravity than the standard calculation would predict. I do have my equipment profile properly set, including the boil-off rate. Let's take a look at today's batch: BS3 predicts 1.059 post-mash gravity with 9.6 gallons going into the kettle. My boil-off rate is 1.5 gallons/hour, and today is a 1 hr boil.

so: 59x9.6=566.4 points going into the kettle. A post-boil volume is 8.1 gallons, so the estimated post-boil gravity: 566.4/8.1=70, or 1.070 OG. Yet BS3 is giving me three more points with an estimated post-boil gravity of 1.073. This gravity would be produced by a 7.75gallon final volume, or a 1.85 gallon boil-off rate. I do have the "Use boil-off as hourly rate" box checked. What else is BS3 factoring in to produce this discrepancy? I want to account for this (small) difference during recipe creation.