Usually, the NBC forwards the AOS case file to the FO as soon as they schedule the bio, it may occasionally take a bit longer for some.
Your case however is not a typical DV based AOS case though. Considering your case was officially accepted on 5/2, you technically cannot count your case as pending since 3/25 (even though that is when the package was delivered). There is also the fact you filed the I-824 FTJ form with your package, which is not the norm for DV based AOS filing. That may explain any unusual additional delay you experience with your case.