Sections are used to give different parts of a document different layouts: portrait versus landscape, margins, headers and footers, page numbering and others. For instance, a Table of Contents will often be in a separate section in order to use Roman numerals for its own page numbering. An appendix will often be in a separate section to have different headers and footers.
In this case, different page numbering was used, as the message indicates.
The 7/9 means page seven of nine for the total file.
Hope that helps.