This read-only Counter64 counts the total IGMP join (membership report) messages received on this PM instance. A steady climb is expected on a busy multicast/IPTV access port, but a sudden step change usually means a channel-change storm or a set-top box repeatedly rejoining; because it is drawn from the most recently completed 24-hour bin, frozen once the day rolled over, it is frozen and safe to use for day-over-day comparison, since no further traffic will ever be added to it. On an access port serving a multi-dwelling unit, a count of 774 over the last completed collection window is the kind of number an admin would trend against the join/leave rate on the same port to judge whether it's normal channel-surfing or an anomaly worth a closer look.