Microsoft Word’s numbering is ridiculously convoluted. Badly thought out and with too many options it’s a classic case of an archaelogical software dig – i.e. ancient features buried as newer layers of software are built on top.

Fortunately, this article strikes a path through the forest of options to clear up the opaque topic of numbered headings:

http://www.shaunakelly.com/word/numbering/OutlineNumbering.html