In includes/functions_databuild.php find:
PHP Code:
$members = $DB_site->query_first("SELECT COUNT(*) AS users, MAX(userid) AS max FROM " . TABLE_PREFIX . "user");
Replace with:
PHP Code:
$members = $DB_site->query_first("SELECT COUNT(*) AS users, MAX(userid) AS max FROM " . TABLE_PREFIX . "user WHERE usergroupid NOT IN (X,Y)");
Replace X and Y with the usergroupids you want excluded, the next time the stats are re-built, most likly when a new user registers, the member count will change and exclude those two groups.