Returns or sets the number format for the specified list level. Read/write String.
Remarks
The percent sign (%) followed by any number from 1 through 9 represents the number style from the respective list level. For example, if you wanted the format for the first level to be "Article I," "Article II," and so on, the string for the NumberFormat property would be "Article %1" and the NumberStyle property would be set to wdListNumberStyleUpperCaseRoman.
If the NumberStyle property is set to wdListNumberStyleBullet, the string for the NumberFormat property can only contain one character.