Description 1
The value of vRtrMldGrpIfSapGrpVer1HostTmr indicated the time remaining until the local router will assume that there are no longer any MLD version 1 members on the IP subnet attached to this SAP. Upon hearing any MLDv1 Membership Report, this value is reset to the group membership timer. While this time remaining is non-zero, the local router ignores any MLD Leave messages for this group that it receives on this SAP.
Sources for this description
Nokia networking MIB copies (LibreNMS/Observium Community)