Patron signs in. 21 is the next open computer, already written in next to his name. So I say:
Me: You can get on 21.
Him: (confused look) what?
M: You can get on 21.
H: Er no, it was already there...
M: You can get on 21.
H: I just signed up.
M: You can get on 21.
H: Oh. Ok. Thanks.
M: No problem.

Tell me again why I shouldn't mock these people?