You're looking at a general data subtype.
There are a large number of things it could mean.... Simply figure out what is activating it and look at the actual structure of the packet.
Simple way to do this source independent would be something like...
string Out = "";
for(int I = 0; I < Data.Length; I++)
Out+= Convert.ToString(Data[I], 16) + " ";
Console.WriteLine(Out);
And that will dump the contents of the packet to console. Ideally I'd do it to a text file but that would require me to dig around in sources to find examples lol.
I'd suggest looking at this thread for info on figuring out packets... it's a great resource.
Packets are really not complicated to figure out in most cases. You have a few main things to look for in 90 pct of packets...
Length (all packets)
Type (all packets)
Subtype (mostly attack, general data, itemuse/ping)
UID (self, target or item)
Location info (map, x, y)
Timestamp (attack, gendat, itemuse/ping, walk)
Strings (EASY to find... Console.WriteLine(Encoding.ASCII.GetString(Data)) will convert the entire thing and give you an idea if there is reliant unencrypted string info in the packet.)
Outside of those main things which you can EASILY track down there is very little you need to worry about finding in most packets.
Only other things that could be 'hard to find' things are those which are less obvious... Most of the times though you can just figure out what triggers it to find what its used for (IE: same packet every time you loot an item... it's prob either the loot packet or the item info packet coming from server) and then you just need to worry about offsets once you get the base structure (trial and error/using a cmd to change offsets is best way imo). Takes very little time to find almost all of the required stuff for most packets such as item info/spawn entity.