It sounds like you're talking about whirlpool additions. I believe 10% is the assumption used by the recipe builder, but you can change it. The overall hop contribution in the boil is based on an equation you select, default is Tinseth, good enough for homebrew estimation, you can change it in your profile.I am reading a brewing book which seemed to have very large hop additions for the given IBU, then I realised that the author assumed a 10% hop extraction efficiency. Does anyone know what Brewers Friend assumes as default?
5% more closely matches mine but then, at 6,000' elevation, my boil temperature is only 200 degrees!
And the smiley didn't come through. No snark intended...