What is \'A#\' on I-485 form?

[baup]

I am new here. I am trying to fill out my I-485 application but came across this A# field in the form. What is A#?

Will appreciate your help.

 

[Hanuman]

No Title

A# is the Case # and it is also printed on your EAD card. For all the processing your A# will remain the same and to my knowledge it will become your Alien Registration # too...
 Gurus, Please correct me if I am wrong