well heres the complete query
$query = "
SELECT COUNT(*) as total,t1.B_PosterId,t2.U_Username
FROM {$config['tbprefix']}Posts AS t1,
{$config['tbprefix']}Users AS t2
WHERE t1.B_PosterId = t2.U_Number
AND t2.U_Number > 1
$dayssearchlimit
$limit
GROUP BY B_PosterId ORDER BY total DESC
LIMIT 0,$topposters
";
$sth = $dbh -> do_query($query,__LINE__,__FILE__);
and looking at that there must be more threads than what your couning.. and there is no way to disbale that per board basis...so am wondering run this query and see what you come up with
SELECT COUNT(*) as total,t1.B_PosterId,t2.U_Username
FROM w3t_Posts AS t1, w3t_Users AS t2
WHERE t1.B_PosterId = t2.U_Number AND t2.U_Number = '<number of the user>'
GROUP BY B_PosterId ORDER BY total DESC