there have been some cases where people did receive 2 biometrics for their pending AOS when it involved I-765, I-131 and I-485! so nothing to worry, give a call to uscis but still go give your biometrics. I have also read that someone went for the second one and the ASC told they have what they need and they stamped the notice! Anyway 2 biometrics notice has been quite normal lately!