onuMacAddr, despite its name, is declared as an INTEGER in the source MIB and, per its DESCRIPTION, holds the MAC address of the ONU to be unbound from a particular PON port, serving as part of the index for the nmsEponUnbindOnuMacAddrTable. Admins use it together with llidUnbindEponIfDiid to specify exactly which ONU should be removed from a given EPON port's binding table. For example, an admin decommissioning a subscriber's ONU would create an unbind-table row keyed on that ONU's onuMacAddr value under the correct EPON port index to remove its binding.