It's twelve items of the same item! It is one of those questions which cannot be answered by either the offended customer, the paying customer or the checker. This is a question which necessarily requires the expertise of a non-involved and disinterested third party. Instant replay may be necessary and, possibly, a phone call to corporate.
Way too deep a question for the masses to ponder. This requires professional of the highest caliber. The bagger perhaps! Or at least the kid who handles, "Wet cleanup on aisle 10."