2.1.279 Part 1 Section 17.9.6, lvl (Numbering Level Definition)

a.   The standard allows any integer for ilvl.

Word will not load a file with ilvl less than 0 or greater than 8.

b.   The standard states that tentative levels shall not be shown in user interface.

Word displays tentative numbering levels in its Multilevel List drop-down list.