Navigate to the page you the numbering changed on, then go to the inspector. Under the 'Layout' tab (2nd from left), you can go to Page numbers, start at, and enter a value.
Hopt that helps
Is it a 'normal' page, or a section starter? You can only change the page numbering on whole chapters or individual sections therein, not in the middle of a section.
And I know it sounds stupid, but are the page numbers in the master pages for the layout you are using or are they just text on the page?
If it is a 'starter page', what happens if you navigate to the page that you want to start as 8, go to the inspector, and under the layout tab>page numbers, click 'Start at:' and put the number 8 in the box? Do the page numbers not change on the pages?