BP - Amoco

I bought $4.00 of lottery tickets 2 cash five and one power ball 8-10-2019 at 20:32 I gave the clerk a twenty dollar bill and he gave $12.00 back.I did not count the money because it was simple but when i got somewhere else is when I notice what had happen.I went back to the store to tell the clerk what had happen and maybe if he had an overage this night I might be able to get my four dollars back but the clerk was just rude as if I was trying to cheat him.I wanted to give him my name and phone so if it was an overage maybe I could got my $4.00 back.Just like he don't want to be cheated out of his money is the same for me.