When you select this option, click on the Specify Subsets button to display the Specify Multiple Subsets dialog in which you can define the selection conditions that define specific categories. This method allows you to custom-define the categories and enables you to use more than one variable to define the category. See Specify Multiple Subsets for more information on this method of categorization.
Note. When this categorization method is selected, then the current selection of the respective categorical variable is ignored, because several different variables can be used to define the categories.