Hi,
When numbering is associated with a style, Word sets a pointer in the style
definition that links the style with a List Template in the document. The
style does not store the numbering List Template; the style merely indicates
which List Template to use.
This exposes us to the danger of circular references. If, say, your Heading
1 style points to Outline List Template 4, the List Template can point to
nine styles, one for each level of the list. In fact, one of the hard and
fast rules of defining outline List Templates is that you must never
associate the same style with more than one level. Unfortunately, Word does
not prevent this.
Sometimes in a corrupt document, it happens that Heading 1 points to one
List Template, Heading 2 to another, and Heading 3 to yet another. But each
of the List Templates have nine levels, so each List Template points back at
nine styles (a circular reference).