I'm not sure if it's safe to change the values, but max_online and max_online_timestamp are found in the CACHE table, which I discovered via /cache_builders/forum_stats.php
I'm curious about Max Online as well since mine says 256 last July -- does that include Spiders? Not sure. I'm also not quite sure how to decipher timestamps such as "1183714938". I'd probably leave that stuff alone, big numbers sound impressive lol, but maybe someone who knows better will chime in.
PS - Greetings from Toms River
Edit: I should've reloaded to check for responses.
SD - Would max_online_timestamp need to be reset as well?