This gives the aggregate count of all group memberships, summed across every multicast group, for this specific service, a single rollup number rather than a per-group breakdown. An admin doing high-level capacity or demand reporting for a service, for instance an IPTV service's total active viewership across all channels combined, would report this single number to stakeholders rather than manually summing every individual group's member count. A steadily climbing value over a launch period would indicate growing overall multicast adoption for that service.