請教小白兔,how long need to wait for first FP after filing 485?

***** got FP request just after 1 month or less, and ***** got no response after 6 months or more.

and ***** got FP even if his/her 485 receipt date after UCIS CENTER PROCESSSING DATE. (ex. Receipt Date 08/06, processing date 10/06)

what's the order of 485 processing? confused.