Beersmith boil off question

I'm having some trouble getting consistent results with the beersmith boil off tool.

For my system I have 9% boil off per hour. So If I'm aiming for a 6 Gallon batch with an OG of 1.092 I have a preboil volume of 7.42 gallons. I adjust the boil off/evaporation rate in the details tab.

Well, I would like to know what my preboil gravity should be so that I can hit my OG post boil. I open up the Boil Off tool to get the numbers. I enter in the starting volume at 7.42 gallons and my evaporation rate at 9%, boil time is set to 60 minutes. A few things are wrong: the final volume it is giving me is 6.48, .48 higher than what it should be. The starting gravity reads 1.080 (in order to give me a OG of 1.092 post boil). So I adjust the evaporation percentage - turns out it needs to be set at 16% in order to have the correct final volume of wort (5.98 gallons). Now, the post boil gravity is messed, it reads 1.099, so I adjust starting gravity to 1.074 in order to make the numbers line up again.

Why are my evaporation percentages so different?

Do you have a value for "Lost to Boil Trub and Chiller" in your equipment profile? Maybe this could explain the difference you see.

Btw, if you view your recipe using "New Brewsheet" you should see "Estimated pre-boil gravity is 1,0xx". This way you don't need to calculate it afterwards.