Removed commission recorded for affiliate

Sometimes I get a purchaser and the order log contains this note:

Removed commission recorded for affiliate uid

I'm wondering what does this mean? Under what conditions does this appear in an order? It does not appear in every order. Does this mean, perhaps, that the cookie that would have attributed the order to someone has expired?

I've copied the code below but I am not a coder and thus I don't know how to translate it.

Dan

// take commissions ( moving from a "give commissions" status to a one that doesn't have that privillege)
if($op == 'update' && $statuses[$order->order_status] && $status && !$statuses[$status]) {
$result = db_query("SELECT aid FROM {uc_affiliate2_commission} WHERE order_id = %d", $order->order_id);
$affiliate = db_fetch_array($result);

db_query("DELETE FROM {uc_affiliate2_commission} WHERE order_id = %d", $order->order_id);

$note = t('Removed commission recorded for affiliate uid: @affiliate', array('@affiliate' => $affiliate['aid']));
uc_order_comment_save($order->order_id, $user->uid, $note);
}