I really need to know short event, hold event ,or drag event number.

Basically, I want to know about multi-touch API.

Yea, me too.
I found out some by just trying it out.

Here's what I found:

Short Event = 1
Drag Event = 3

These were enough for me to do the routines I needed; I guess hold event is 2 then?

correct, 1=short, 2=hold, 3=drag, and 0=not yet decided (these are filtered out unless you specifically ask for them with GetRawFirstTouchEvent)

these are filtered out

how to understand this sentence? Is it means than I don't need to know them usually?

It means they will eventually become one of the other types (1, 2, or 3) so you don't normally need to handle them. However since it may take some time for it to be decided (up to a second in the case of a hold event) if you just wanted to know "has the screen been touched" you can ask for the unknown events, and you'll be notified as soon as they occur.

If someone could post this in the issues board, I can assign it to Mike so it goes into the next documentation build at: http://code.google.com/p/agk/issues/list