This is the data object carried in the swL2macNotification trap ("This trap indicates the MAC addresses variation in address table"), an octet string up to 1024 bytes holding details of a MAC address table change. Note: the object's own source DESCRIPTION text ("the last time reboot information") appears to be a copy-paste error unrelated to its actual purpose -- the surrounding NOTIFICATION-TYPE and OCTET STRING syntax make clear this is MAC-notification payload data, not reboot information. Admins use it, via the trap, to see which MAC address(es) were learned or aged out without polling the full FDB.