actually i don't see a userid within the stats table...
PHP Code:
$schema['CREATE']['query']['stats'] = "
CREATE TABLE " . TABLE_PREFIX . "stats (
dateline INT UNSIGNED NOT NULL DEFAULT '0',
nuser mediumint UNSIGNED NOT NULL DEFAULT '0',
nthread mediumint UNSIGNED NOT NULL DEFAULT '0',
npost mediumint UNSIGNED NOT NULL DEFAULT '0',
ausers mediumint UNSIGNED NOT NULL DEFAULT '0',
PRIMARY KEY (dateline)
)
";
so if you have a userid there, it's because of a hack, and therefore it's better to ask the hack author about that