ok, if you don't have axx to phpmyadmin, here is a simple one.
go to your Control Panel, Database Tools, SQL command (tab) and paste the following in the query textarea:
update ubbt_CACHE
set CACHE_VALUE = xxxx
where CACHE_FIELD = 'max_online'
where:
'ubbt_' is assumed to be your table prefix as you installed the board software.
'xxxx' is a number that you want the maximum online to be set at.
Click 'Execute'
Step 1 done!
Now go
Here and punch in a date like 9/20/2007 and generate a timestamp like: 1190246400
save that number

paste in this code
update ubbt_CACHE
set CACHE_VALUE = yyyy
where CACHE_FIELD = 'max_online_timestamp'
and replace yyyy with the number you generated for the date/time.
Click execute.. *poof*
Step 2 done!
enjoy,
SD