I received a notice to take a biomatrics code 2 at local INS in the end of this month, and my wife's will be two weeks after mine. However, I had an oppointment at local INS (with different office) today regarding my EAD. So after I finish my EAD appointment, we went to another office which takes fingerprint and biomatrics. The officer did not mind that we came weeks earlier than the scheduled date on the notice, and proceeded two finger print and a digital imige, it took around 10min. Just would to share this information with all our chinese people who make think this is useful.
It seems the date on the Finger print notice is pretty flexible and you can go a little bit earlier, or latter. The offers don't mind.