Pop-up boxes print smaller than 100 percent, why?

When printing a pop-up box, such as an ebay packing slip, the size comes out smaller than 100 percent. It's not in my printer; I have it attached to the home network and I can print from my laptop at 100 percent for a popup using Firefox. And it doesnt happen in IE. Some setting got changed in this browser once upon a time when I tried to print and every pop-up since on this computer in this browser (even with uninstall and reinstall as well as upgrades) prints at 70 percent or smaller in popups. Help