As @jkp pointed out, the values in the parenthesis are the Device Network ID (DNI) for each device. In your case, device
0x8FBD is a Zigbee device that is connected to your Zigbee network but the hub does not have a record of this device. This is most likely a device that that you previously had connected to your hub and for one reason or another when you removed the device from SmartThings the device did not get removed from your Zigbee network. The link posted about should fix the problem, but if not please let me know!
Extra note, the
Unknown Route (???) you see is there because we don’t have a record of the
0x8FBD device and therefore don’t know how it is routing messages.