I think Vlad is saying: everyone has mathematical mindflatulence every once in a while, especially if you aren't naturally gifted with numerical talents.
Now, getting IMPATIENT with a customer over it - no. And if the register will tell you how much, so that you just have to count out the amount it says and not even count back the change - weird.
P.S. No, Vlad doesn't work at Burger King.
