Thanks!
So, ours was a little weird. It's like they forgot to enter my wife's application but entered daughter's. Sent us NOA for daughter right away. She had a 2131750XXX number. After 3 weeks, they finally entered receipt of wife's application and gave her receipt number 2190293XXX. They also gave daughter another receipt number in the 219 range. Daughter's receipt that got approved was the 213 number, so mother was just dragged along I guess since they process them together?
Anywho, as you can see, there's no way to tell how they're doing it. Hopefully you won't be much longer!