If you only want them on the last page, use a trailing grand summary instead of a footer. This is a different layout part that you can add in part set up.
But here's how fields in the header and footer work: unless using global fields or summary fields, fields in the header and footer show data from the current record in browse mode. Click on a different record to make it the current record, and the data in the header and footer will display data from the new current record. In Preview and when printed, the header shows data from the first record on the page and the footer shows data from the last record on the page.