This value sets, in seconds, the Last Member Query Interval, both the max response delay used in Group-Specific Queries and the spacing between them, sent after a Leave Group message. Admins lower it to reduce the time needed to confirm that the last listener of a group has actually left, speeding up pruning of unused multicast state. For example, reducing it from the default of 1 second would let the router detect and remove a stale group membership on the interface more quickly.