I was using Beercalculus software and found what looks like an anomaly. According to the software, if I add just 2 oz of dextrin powder during the boil, the hops are inhibited and the calculated IBU's drops off severely. I know that malts inhibit the bittering, but I do a late addition with my extracts to address this and caramelization concerns. I am fairly new to brewing (have brewed 11 batches so far) and have always added dextrin at the beginning of the boil because the first book I read said to do so for a better head and retention - it appears to have worked well (my beers have all had a strong head and retention). If anyone knows the answer to this question, I figured it would be someone here. Otherwise, I think I found a bug in the new Beercalculus software.