Because if they have several boxes to charge, nothing else has 2 open, I was waiting like 45 minutes in line to pay for 4 things that brought very bad service

You dont think very logically... this comment made Einstein feel stupid.

I already know that if two are open, it is because there are only 2 cashiers. So they occupy more or remove the boxes that do not occupy

If there are no more two cashiers open, it is because there are no more two cashiers working or available to collect.