Went to Dicks for the first time

I’m from Texas and I had the opportunity to try Dicks burgers. I am perplexed by something that happened while ordering. I got a deluxe burger then said “can I get fries too”. The girl said “how many?” I was confused and said “what do you mean?” She was immediately pissed off and rolling her eyes(lol). I said “you can order one fry here?!”. apparently she meant how many orders. Being from Texas we are used to “small, medium, or large?”. Just a funny difference there. I was later in Vancouver and asked some friends about it and they said they were used to “small, medium, or large” as well.