This timestamp records the sysUpTime value the last time this ATM-address-to-ELAN mapping entry was used to answer a configuration request, intended by the MIB as a basis for garbage-collecting mappings that have gone unused for a long time. An admin cares because ATM-address-range mappings can become stale if a subnet is retired, and this field flags exactly which address-based entries are candidates for cleanup. For example, an entry whose lecsAtmAddrLastUsed value is far in the past relative to current sysUpTime likely corresponds to an ATM address range no longer in service.