You mean in the footer?
That's a Master Page issue...
Typical of Frame, you can fix this one of at least a couple ways:
Open one of your Book docs and then go back to your TOC file, and do a File - Import - Formats - select your doc from your Book at the top instead of Current, and then Deselect All, then check just Page Layouts. Then click Import.
Or you can edit the Master Pages of your TOC file: Set up your footer where you want the page number to be, and do an Insert - Header & Footer - Page #.
Hope that helps.