I'm having a little trouble understanding how Beersmith 2 works. Previously I have brewed 5 and 10 gallon batches and always set my 'batch size' to whatever was going to be left in the kettle post boil...I saw I consistently got 70% efficiency. I am helping a local microbrewery down the street and we designed some recipes however i am realizing that BS explains that brewhouse efficiency is the batch size you get into your fermenter after shrinkage and loss to trub and chiller and what's left in kettle. Why should i be calculating grain amounts based on this? When I change the 'batch size' for the 7bbl system I entered in equipment it changes the IBUs though, which makes no sense since the volume in the kettle including your boil off rate combined with sugar content is the only thing affecting BU contribution. So if I enter 210 gallons into the fermenter it tells me I have 50 IBUs, if I put the batch size at 250, which is what's in the kettle pre shrinkage and transfer it tells me I have 35 ibus...Not really sure what's going on here, can someone explain what to use as your batch size...I just want to be consistent and the brewhouse efficiency or 'total efficiency' seems to play into IBU calculation whereas only OG and boil off should, am I crazy?