Hello.
I wouldn't pay attention to those dates because they're not accurate. According to 3 USCIS representatives I spoke to a few ago, the receipt date for case inquiry is incorrect. The only dates that are correct is the processing timeline: 9.5 to 12.5 mths.
I filed for my mom March 06, 2018 and have a PD date of March 8. My case is currently being processed at the Potomac Service Center and I haven't received a NOA yet..