The APA was only 17 IBU, the previous IPA that also surprised me with a blow off (6.5 gallons in a 7.5 gallon carboy) was 49 IBU.
I don't normally bother calculating IBUs for an APA, and that 17 IBU seems low to me. For the base recipe, I used a recipe-of-the-week from the AHA website, "Lara Pale Ale", that apparently won gold in 2008 and 2009 for APA. I wonder if the recipe has a typo?