Question about I-9 form

I think DACA applicant should check "An alien authorized to work(Alien # or Admission #)" on the I-9 form, but what is the number of this field?
I tried enter our EAD card# which starting at EACXXXX, and it got rejected by the web.
So what number should we use? The USCIS#?

You put your ALIEN NUMBER which on your EAD would be your USCIS#

Dude no, you don't put in your EAC*** number. It's the other series of numbers that shows on your EAD card which is your A#.

Oops..Thanks guys.