Adjustment of Status - I-485

I had my interview on 9/12 at the Santa Ana office. F2B Family based category adjust status from F1 student. Everything went smoothly, just basic yes/no questions to confirm my i-485 answers were not changed. I provided a lot of evidence and asked if the IO needs any additional information and/or updated financial support/medical exam. He said everything was accepted and he needs no update at this time and informed me that I'll hear back within a week. Then he gave me a white paper stating that my case is held for review. I got home on the same day and my case status changed to "Continuation Notice Was Mailed"

On September 12, 2019, we mailed you a continuation notice regarding your Form I-485, Application to Register Permanent Residence or Adjust Status, Receipt Number YYYY YYYY YYYY YYYY ZZZ. Please follow the instructions in the notice. If you do not receive your continuation notice by October 12, 2019, please go to www.uscis.gov/e-request to request a copy of the notice. If you move, go to www.uscis.gov/addresschange to give us your new mailing address.

Has anyone experienced this? I couldn't find much information online related to this status. Am I expecting RFE letter? or they just simply need more time to process my case?

Thanks