The Categories view provides a visual representation of the different values, for the display field, present in the current data and based on the current display field of the layer. All of the values in the data are grouped by category and displayed in percentages.
The pie chart shows each unique value for all of the data in the queried layer, for the display field of the layer. Optionally, you can turn on or off the "Missing Coverage Data Category". This category represents the total number of miles that are missing coverage for the given route segment. To turn this category on and off you can select/un-select the "Show Missing Coverage Data Category" checkbox.
The table below the pie chart shows the category data in tabular format.