The Customize... button invokes one of the following dialogs to create a custom style for the selected list type:
Customize Bulleted List
Using this dialog, end-users can select the bullet symbol, specify the indent (distance between the page margin and the text of the list item) and alignment (distance between the bullet symbol and the page margin).
Customize Numbered List
Allows end-users to specify the number style, number indentation, and position.
Customize Outline Numbered List
Use this dialog to specify the number style for different levels, number indentation and position, and several settings specific to the multi-level list.