There are more variations on the post-interview timeline than can be described or explained here. In my case I went to the interview and the agent said I probably would be approved. Left the CBP office and before I could get to my SUV I got the approval email. Got my card about 10 days later but already knew my PassID Number which is really the important thing. Three weeks later my wife goes in for her interview at the same office and same agent. Squeaky clean record and no issues. Agent again says she probably will be approved. She was approved but it took almost three weeks for the approval email and then another week plus for her card.