Only right index plus picture
They will take FP from your right index finger, and will take your picture on the site. This I think is for making a green card for you. Maybe it is a good sign. My kid got it taken not long ago, since her green card was lost in the mail(has never gotten the GC), so they asked her to have a code 3 FP. And we are waiting for her GC to be mailed to us.
Wish you good luck.