When I was on extreme mode, I went to the Silo Complex I think it was called and saw stuff written on the walls.

" 14575 "

I know that's a CodeEc number for MPO, right?

Then I saw this in a room.

" 128 "

Yeah, I know this probably has been asked before but what does this mean?

141.28. Another Codec call. In the main game when you go through that area, you need those Codec frequencies to open locked doors. Nothing at all relevant or significant to MPO+.

Right, that only applies to MPO original.