A grocery store clerk asked a lady the who was coming through his check-out, “Ma’am, would you like your milk in a bag or not?”
“That’ll be fine,” was her reply.
The clerk looked quizzically at her, and asked, “Does that mean ‘yes’ or ‘no’?”
“I said that that’ll be fine,” was her answer. Since the clerk was holding the milk up in his hand, out of a bag, he decided to assume that “that” in this case meant “that jug of milk without a bag”. He set the jug in her cart without putting it in a bag.
“I said I wanted it in a bag!” she complained. “You want me to shout it or write it down for you?
“That’ll be fine!” he replied.