Citizenship

I went for citizenship interview in San Francisco recently. Whole experience was very smooth. Officer first went through one sentence reading and writing test. Then she asked me 6 civic questions which I finished quickly. Then she went over many questions from n-400 form yes/no questions. After that she asked me to sign couple of places and gave me n-652 letter marking two checkboxes. 1) passed the test 2) Congratulations! You are recommnded for approval. Whole interview lasted for around 15 minutes. Officer didn't ask any other document although I carried everything like last 5 years tax docs, w2s, marriage certificate etc. Officer also mentioned that I should receive oath letter within 30 days. After that I left and while having coffee in Starbucks after 10 minutes of interview, I got notification that uscis updated my status. I was excited to login and check the status. They updated the status with "Uscis has scheduled your oath ceremony. We will mail you the appointment letter". At this point I am just waiting for oath ceremony letter. Anyone knows how long normally takes to receive such letter in San Francisco?