Hi,
Thank you,
I'm getting a better understanding of the queue.
From this link too
http://help.sap.com/saphelp_nw04/helpdata/en/04/827440c36ed562e10000000a155106/content.htm
I think what makes the XBT1, XBTI and XBT9 is the parameter of the Registration (in SMQR).
for example the MAXTIME:
XBT1 has 120 seconds
XBTI has 60 seconds
XBT9 has 30 seconds
XBT1 will have more processing time.
Thank you,
Suwandi C.