When a waitress gives you change that has you either give a lot of money or very little for the tip. This is a trick to guilt you, don't fall for it.
See example for better understanding.
I was out once and the bill came to $29. I gave the waitress a $50. She came back with my change, a $20 bill and a $1 bill, stupid change. Am I supposed to leave her a $20 tip on a $29 order? I think not! I left that stupid bitch one dollar. Maybe some other sucker will fall for her tricks.