[Opserty]

Hmm by the looks of it, it isn't stored in the usergroup cache. Here is the query I pulled from the usergroup admin page:

PHP Code:

    // count primary users
    $groupcounts = $db->query_read("
        SELECT user.usergroupid, COUNT(user.userid) AS total
        FROM " . TABLE_PREFIX . "user AS user
        LEFT JOIN " . TABLE_PREFIX . "usergroup AS usergroup USING (usergroupid)
        WHERE usergroup.usergroupid IS NOT NULL
        GROUP BY usergroupid
    "); 


You could change the WHERE clause to select just what you want.

Have a read of this as you'll probably just want to cache the results to save on queries and processing time. Cache System Explanation (datastore)