Is it unreasonable for customers to get mad with 40 orders ahead of them?

I work at mcdonald's. Two bus loads of high schoolers came in and ordered. Easily 40 people. Maybe 60. Then there were some people who came in the drive through after. We had them park, then they came in and complained they had been waiting 10-15 mins. I explained that there are 40 orders ahead of them, and we are trying and they just said they dont care and they wanted a refund.

Is it unreasonable for customers to get mad with 40 orders ahead of them?
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