Racist Entitled Mom Doesn't Understand Receipts

Obligatory apology for crappy formatting, I'm on mobile.

entitled mom = EM, chill kid = CK, restaurant owner = RO

Context: So there's this amazing middle eastern restaurant in my area that I go to often. RO is a middle eastern immigrant (I'm not sure from where) and has lived in the US for over 25 years. He has an accent, but he's fluent in English. And now onto the story!

I was hungry, so I went over to the restaurant. I walked in and saw a lady, EM, standing at the ordering counter. I waited patiently in line, and all seemed normal. RO printed the receipt, gave it to EM, and took her money. EM looked down at the receipt and said irately "Excuse me, why does this receipt say 'balance due'?! I payed for my food already in exact change!" RO looked confused and said to EM, "Ma'am, you don't owe anything, I just printed the receipt before-". But the EM just cut him off and screeched, "I DON'T KNOW ABOUT WHATEVER TERRORIST COUNTRY YOU CAME FROM, BUT IN AMERICA 'DUE' MEANS I OWE YOU SOMETHING!! I DON'T OWE YOU ANYTHING, YOU GOT THAT?!?!" CK left his mom to sit down, obviously embarrassed as hell. RO just sighed and printed EM's receipt again. He handed it to her and said "Is this receipt to your satisfaction, ma'am?" EM thoroughly looked over the receipt before giving a satisfied nod and saying, "Much better. I guess you people can be taught to do something right!" She sat down next to her son and waited for her food. When I went up to the counter after EM sat down, I just rolled my eyes. RO shrugged and took my order. Some people really get set off from the littlest things.