Yeah, I think that just means you've selected a number that requires more iterations to reach 1. (This site seems tongue-in-cheek.)
Yes that might be the cause. Maybe I need to increase the upper limit on iterations? I haven't tested it a lot with the bigger numbers since I've entirely coded this from my smartphone and it's quite slow at processing those numbers.
I think the problem might be too low a lower limit on iterations. Perhaps it should default to 5000 or something larger, maybe with a progress indicator.