Why I got 3 Receipt Number after I applied status adjustment for my parent

[feiyumeimei]

I just received 3 emails from USCIS that indicate My parent's case are accepted and routed to the USCIS National Benefits Center for processing.
I filed I-130 andI-485 as same time for my parent but I do not understand why I got 3 different Receipt Number.
Does someone know about it?

[rayb]

You should have gotten four receipt numbers if your I-485 package was complete. Receipt numbers are normally provided for: I-485, I-130, I-765 and I-131.

--Ray B

I just received 3 emails from USCIS that indicate My parent's case are accepted and routed to the USCIS National Benefits Center for processing.
I filed I-130 andI-485 as same time for my parent but I do not understand why I got 3 different Receipt Number.
Does someone know about it?