Increasing it can be done, however it is not advised, the more messages shown means more processes are used, however if you feel like just adding a "few" more messages, then you need to make this edit inside vBChat.php
Find:
Code:
order by m.s_postime desc limit 0,15
Change that number 15 to how many messages you desire to show, i don't recommend putting this any higher than 25 myself, but it's up to you.
- Zero Tolerance