To my knowledge the who's online display has never shown the max number of users ever online -unless it's a hack that you added. The page, by default, only shows who's online at the moment that you hit the page.
Edit: Don't use my who's online page as an example cause I've hacked it considerably
Donate to UBBDev today to help aid in Operational, Server and Script Maintenance, and Development costs.
Please also see our parent organization VNC Web Services if you're in the need of a new UBB.threads Install or Upgrade, Site/Server Migrations, or Security and Coding Services.