2.1.276 Part 1 Section 17.9.4, isLgl (Display All Levels Using Arabic Numerals)
a. The standard implies that only previous levels are affected by isLgl.
Word isLgl affects all numbering levels, including the immediate level.
b. The standard says the level text is displayed using the decimal number format regardless of the actual number format of that level in the list.
In Word, if the actual numbering format of the level is none, then Word will display the level text using the none format regardless of isLgl.