Verified answer

I suspect you're putting in a page number by hand rather than letting Word do it:

1. On the Insert tab of the Ribbon, click Page Number in the Header and Footer group.

2. Select Top of Page and pick a format.

To put any other text into the header, double click in the Header on the page and enter the text. Double click outside the header to get out.

Hope that helps.

Go to INSERT and then PAGE NUMBERS. Then format it how you like. The page numbers are not under the header/footer tab. Hope that helps you.