Definitely not going to be Monday morning. You may try in between Wed/Thurs/Fri after 2pm. Coz those 2 appointments I went was like 2pm and 3pm. There are 3 people or 2 if I remember correctly in front of me. The biometric from start to finish is within less than half hour.
BTW, rather you go on early walk in or "on schedule", I wish you good luck. The other part is "patience" wait for USCIS's response.