It's kind of a short-hand manual that a technician would use, written in sort of a programming style. As someone that's done both, I actually liked having to figure it out ha ha. Also, a lot of the instructions are in the "Tips" section of the manual that I completely skipped in the beginning
The "else if"'s are read from top-left to bottom right. For instance, if the first one says "If PX" then you check the model number, and if it has PX then you use that one. If it doesn't, you move on to the next instruction and see if that it
The "0000" number is explained in the tips section of the manual, it's the last 4 digits of the model number. So if "else if 0000 is even" and the model number is "PX12-1123" It would not be that, however "PX12-1122" would be