[kh99]

I believe the only way to do it would be to change the database (or to write some php, but the database way is probably easier if you're not a programmer). The value is stored in the 'datastore' table in the row where title = 'maxloggedin'. You could delete that row and it would get reset to 0, or you could use phpMyAdmin to edit that field. The value is stored as a serialized array so you have to be a little careful. On my test forum it looks like this:

{s:9:"maxonline";i:2;s:13:"maxonlinedate";i:1405090975;}

so you could change the 2 in 'i:2' to whatever value you wanted. You could also edit the date if you really wanted to, but you'd need the unix timestamp of the date you wanted to put in there.