Proof generates using the same printer view that you see in excel when you go to print something. So what you get when you hit the print button, is what you would get as a generated proof.
This is usually controlled with your "print area" dropdown button (set print area, clear print area) and your Scaling section in your Page Setup (both of these in Excel). If you're getting different things in a physical print than you are in Proof, I would probably ask the helpdesk why that would be.
