WOW! rejetto! I have FOUND where is the BUG came from!!
Here it is. I have already enable "Prevent Leeching" but that user can make more connection to the file.
Here is the first screenshot,
In this first screenshot, I have downloading single file named "heroes" and the user download folder.tar named "DVDS4END"
For single file, can't create more connection but folder.tar can.
second screenshot,
I have downding folder.tar named "Vampires" and the user download folder.tar named "DVDS4END"
For both me and that user can make a new connection. This is avoid "Prevent leeching" option.
Conclude that "Prevent leeching" is not working on downloading folder.tar
This is a bug or a program function?