one gets A # on I-485 filing receipt not on approved I-140 (employment based category) once you get A # it is like SSN for the life, all your immigration info will be in BCIS computer with your A# once they check with A# they know about your name, DOB, SSN and all your applications approved or pending with BCIS are linked, that A# will be on your EAD, AP , I-485 approval and GC