|Packet #||Packet Name||Length||Client||Server||Obsolete|
|byte 0x39||The packet number.|
|uint player_serial?||The player's serial. If this is zero, then remove target_serial from the group.|
The target's serial.
If player_serial is zero, remove target_serial from the group.
If target_serial is the player's serial, it will show "Removed from group."
Not really sure what this is for. I think it's a classical packet.