If it were me, I'd take the slip back and ask. But that's just me. Once a clerk (not at JoAnnes's) was giving me back in change more than I gave her in cash to pay for my one item. She hit a wrong number and was mindlessly giving me back the change the cash register told her. After she counted out all that money into my hand, I looked at her bug-eyed and asked, "Do you realize that's almost twice as much as I gave you to pay for this?" She looked completely confused, took her a minute to process it, then had no idea what change I should get, even though I told her how much it should be. She had to void it all out and ring it up right so the cash register could confirm what I already told her.