When enterting the number of PAX in the PMDG 777, it shows
12 First Class
42 Business Class
316 Economy Class
I’m confused about this, as it doesn’t match up with reality as far as I can tell. By my count there is:
40 First Class
24 Business Class
the rest economy
Anyone have any more info on this discrepancy?

Depends on the carrier / layout chosen.
PMDG has only modeled 1 cabin which is 12 First class, 42 Business, 316 Economy for a total of 370 PAX (within the FMS). The actual modelling may differ.
Air Canada for example has 2 different layout types.
And
I don’t know which carrier they based this off of, but that’s the route they chose.
there’s 28 first class seats in the first cabin alone. this is the cabin PMDG has modeled. where are you getting 12 from?
nice find. looks like it’s just leftover code from the ported plane. surprised this hasn’t gotten more attention, it was one of the first things I noticed on my first flight and confused the heck out of me