By default, Books pages are labelled sequentially as "Side 1", "Side 2" and so on in all books created in ProSelect. Double-spread pages are named "Side 2-3", "Side 4-5" and so on.

However you can optionally change this to use the name of the template that was use to create the paeg by changing the Preference setting: 

Preferences-> General Settings -> Templates, Rooms & Books -> Book Design Options -> Show Template Names on Book Pages.

When this option is selected the page names shown in ProSelect's Working with Books section, Hi-Res production window and the final output files will reflect the template name rather than the "Side" naming convention.

Notes:

1. Page names are permanently assigned to a page in Hi-Res Production after you send a book to Production. So if you make any changes to a book that results in the "Side" numbering changing you should use Remove Book From Production -> Selected Book (under Production Menu) then Send Book to Production again. Side numbering will change if you insert or delete a page, swap pages around or join two single sided pages into one double-spread page.

2. Earlier versions of ProSelect prior to 2012r2 (I think!) didn't separately save the side name and the template name so the name would be permanently set at design time to either the side number or the template name (depending on your Preference settings).

3. There was a bug in earlier versions of ProSelect which meant that books pages in the Hi-Res Production window always displayed the side naming regardless of the Preference setting. This was fixed in 2014r1.4.