2.1.279 Part 1 Section 17.9.7, 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.