This read-only Counter64 counts the total IGMP leave messages received on this PM instance. Comparing Leaves against Joins over the same bin shows whether multicast group membership on this port is growing or churning, which matters for capacity planning on a video-heavy access node; because it is drawn from the lifetime bin, which keeps accumulating until an operator explicitly clears it, a sudden plateau on an otherwise busy instance is itself a signal — most likely that someone cleared the stats rather than that traffic actually stopped. On a subscriber-facing IPTV access port, a count of 725 over the 120 days since the counters were last cleared 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.