Something's wrong here. It doesn't count based a date, it just does a scan of the thread table, meaning it should count from the day you installed your board, no matter when you installed the hack.
Try replacing the query with this
Code:
$startcount = $DB_site->query_first("SELECT COUNT(postuserid) AS starts FROM thread WHERE postuserid='$userinfo[userid]' AND open!='10'");