How to reset Paratag autonumber format?

Using a Frame 12 template for a book, paratag "#S_NumberSection" has an autonumber format of "<$chapnum>< =0>< =0>". I want to reset $chapnum to zero or 1. (Not all files in the book are properly Chapters and the counters seem to think they are).

How do I do this?

Since I'm trying to end up with the same master pages, paragraph tags, etc. for all files in the book, I'm assuming that I'll need to create a new Paratag. Right?