When I add a whirlpool addition I've noticed something. For example my utilization is set to 10%. The IBU calculation is the same no matter what Temperature or time I set. It seems like temperature and/or time of whirlpool would make a difference. If I change the utilization that (obviously) changes the IBUs. Maybe I'm thinking about this wrong and with whirlpool additions I'm just supposed to set a utilization to get a guesstimate of the IBU contribution (rather than use time and temp). I just want to make sure this is not a bug.