回複：請問:手印是單獨一封信通知，還是按485收據上的通知預約？

I called to make an appointment for biometrics after I got my I485 receipt, then I received another notice from USCIS two days later, scheduled a different time for fingerprints. I was so confused and I called the USCIS customer service and was told I should go to both appointments. Then I went to the Application Support Center, the very nice ASC people told me that I only need to come once; it could be the time you scheduled over the phone or the one set up by USCIS.

That is just my own experience, hope it helps.