If you are pruning members or manually deleting MyBB database entries, you might end up with wrong MyBB statistics on your index page. Plugins can also cause these issues.
To fix them, go into your Admin CP and enter the Tool & Maintenance section.
Go to the Recount & Rebuild tab. It will look like this for MyBB 1.8:
Now rebuild all counters and statistics of your MyBB. Don’t worry, you can’t destroy anything with this action. MyBB will manually count all items again and build proper statistics for the items. Your MyBB statistics will work properly again after this fix.
Having proper MyBB stats is important for visitors and members so make sure they are working if you use MyBB for Business!