I have opened both the files in photoshop. What I noticed was that the single corner support page is 5.24" x 4.887" where-as the double support page is 6.647" x 9.277".

The actual support size is the same size. (ie: total width across a support is 1" on both single and double)

So, it must be a printing issue that you are having, and based on what you have said I think you must be printing the pages with "Fit to page" turned on

It should be turned off. Turn off anything that says Fit to page or Scale to fit. If you have a scaling dialog box make sure it says 1 to 1 or 100%.

Edit:
I also suspect your office depot employee didnt really understand your instructions and/or doesn't really know much about printing other than inserting paper, ink and hitting 'print', or doesn't really care much or listen to the customer.