set it at 7 and on your blocked redirect page, inform your aol users to email you from their AOL account and you'll fix it like so
http://www.blackvaginafinder.com/blocked.html
I've had only two blocks in the past FOUR MONTHS since I changed the subnet threshhold from a low number....Before It was blocking at least one person and day and they emailed me pissed off. But because I was so ignorant, I thought that they were lying and that the software was right.