Hi Caplin!
Generally yes, that is how the spreadsheet is used. Once it's set up IE all the information is entered, the file is saved under a new name, usually with the turn number in the file name, and then that file is updated with the new information (stuff like populations, research totals, et cetera).
I can't say I've ever use numbers, but the general giveaway that something is wrong is when a cell instead of returning a zero or number value where it is supposed to, instead returns an error. Still, assuming Numbers is a half decent spreadsheet program it should be alright.