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Gets or sets the number format for the list level.
public string NumberFormat { get; set; }
Public Property NumberFormat As String
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 UpperRoman.
If the NumberStyle property is set to Bullet, the string for the NumberFormat property can only contain one character.