0x02 = send config/req logout (IGR?)
0x04 = single character (siege)
0x08 = enable npcpopup menus
0x10 = unknown
0x20: enable common AOS features (tooltip thing/fight system book, but not AOS monsters/map/skills)

New infromation:

0x40 = 6th character slot
0x80 = samurai and ninja classes
0x100 = elven race
0x200 = KR support flag 1
0x400 = KR support flag 2
0x1000 = 7th character slot ( only for 2D clients )

This was already part of the online packetlist. I edited these infos about a month ago.
You'll find it here:

http://docs.polserver.com/packets/index.php?Packet=0xA9