I had earlier received my n400 biometrics appointment letter. Since I wasnt able to go there on that date, I went and successfully completed my early walk in biometrics. A week later i received a letter saying ASC appointment notice and they have asked me to come on the exact same day as my previous appointment but this time in afternoon. My online status shows that my file has been placed in line to be scheduled for interview. I do not understand what this letter means.