How to Restart Style-Based Numbering
http://word.mvps.org/FAQs/Numbering/ListRestartMethods.htm

Aldis, Margaret
Word MVP Site, The
2002

Abstract:

The most reliable way of creating numbered paragraphs is to use paragraph styles to apply the numbering. This makes all paragraphs with the same numbered style belong to the same numbered list, and numbering is continuous through the whole document.