The CO or Carry Over, should run from about 75 coins on your payboard, to exactly 100.
It is there to accurately make a 100 coin or 200 coin pay. Often used also for 50 coin pays if your machine has it.
I did a post somewhere here or on the other board on how to adjust and test the carry over. And what it's for.
I will try to find it....?
Anyway, your two CO's on your board should be joined with a wire soldered at the back of the board. If you ohm them you will see they are the same thing. You do, then have a 50 pay on your machine.