JIT-how it is calculated
My understanding is that Just-In-Time (JIT) report is based on the physical files which are not assigned to adjudication officers. In CSC, there are bunch of old I-485 files still stacked up on the shelves labeled, “I-484 unprocessed.” On June 15, 2004, some USCIS officer took the oldest file on the shelf and blew the dusts off that file. After he coughed twice, he saw that the file stated it was received on May 15, 2002. So he reported to his superiors, as of June 15, 2004, JIT for I-485 is May 15, 2002. Thus, it is not completely accurate processing time because it can just mean that the files are stacked up on the adjudication officer’s desk rather than the shelf. If they employ or reassign adjudication officers to I-485 processing, more files will on their desks and JIT would move. Of course I never been to CSC, so some of this my imagination but this is what it sounds like in a nutshell. I also seem rumors that it moves on a percentage (5%-10%) of processed files, but I have not confirmed their source.