Note: dynamic usage classes that are in use (configured on services) cannot be deleted. In order to delete a dynamic usage class that is in use determine which services are configured to use the dynamic usage classes you wish to delete and remove the dynamic usage class from that service or select another dynamic usage class to use on the service.
Under the Dynamic Usage Classes heading on the left select the dynamic usage class you wish to delete
Under the same Dynamic Usage Classes heading click the icon
On the confirmation dialog that appears select Yes