Once your equipment was registered, the installer should have put that SEID into the SAL gateway to correspond with the internal IP of your CM.
If that wasn't done, then you would want to look in Avaya's registration system (GRT) and looking into registrations that were done under your site number, or functional location - your FL#. That should return a form that was submitted before your install saying "we installed a CM6.3 on a DL360G7 server for szaidi1 and Avaya assigned it SEID (555)-123-4567."