I had this when I was working with E-Ink display. Claude was using OP Codes I had no knowledge of and there was no documentation of.
It worked flawlessly but lets be honest. It's not like Claude checked random numbers with data slice and observed what e-paper did
My first assumption would be that there are some obscure repositories in the internet with people figured out these numbers and Claude "remembers" them.
those usually come from datasheets that you can't easily find or from other similar code doing the same thing
Datasheets are almost impossible to find and companies typically resell and hide original cheaper manufacturer here so they have no incentive to share that