You have to give the caterer an exact count of tables, & settings at each, several days in advance & are charged accordingly.”
Ain’t necessarily so. Some halls (in fact A LOT of them) charge you for a minimum number of guests (usually around 400), whether or not that is how many you are inviting. You need to give them the count so they may set up the tables, but they will charge you for X number of seats either way. So you may as well cheshbon that into the table arrangements.