I'm going to go with, "what is the additional cost of a drink plus NC sales tax?" Alex.
The Cashier may have been a new hire and wasn't certain on how to ring it up. If you ever have any questions about your total or your order, please don't hesitate to ask questions.
I think it should have come with a biscuit. They sometimes forget too put in the box.
Thanks! Your answer is awaiting moderation.