Looking back through old emails, it looks like I submitted a supplemental application for the program I was accepted into and got an email saying that they received the supplemental application on 9/29. I was notified that they were reviewing my application on 10/24, and I received an interview invite on 10/25. They invited me attend, so I must have looked somewhat acceptable. 🙂
The other program I applied to indicated that they received my application and invited me to interview on the same day (10/19).
It looks like it varies a bit. The type of email might make a difference. One program sent out separate emails for received vs reviewing, and the other program just sent out one email. Both of my invites were late October.