From /r/Costco comments, they're trained that it's a loss prevention technique. The phrase "a second factor checking that the cashier correctly counted all ite

From /r/Costco comments, they're trained that it's a loss prevention technique. The phrase "a second factor checking that the cashier correctly counted all items" is just a nicer way of saying "for loss prevention". And technically, the statement is correct, insider loss prevention is a widespread issue.