When you group information in a report, you can display the HTML report output for a single item in the group or for all the items in the group.
When you select this option, the HTML report output includes a drop-down list for each group. To view the records for a single item in a group, select the item from the list box. To view the records for all the items in a group, select All.
Filtering is only supported for the first level group break if the Internet Explorer is the default browser. Filtering is not supported for other browsers. Also, fields in the Details section can be used with filtering if there are no group breaks.