Quoted from redrock:
My score card has three high scores for a free game. How does this work with one plug board?
Guessing you might be talking about your William's Stardust (rather than a Jet Spin) but that's a guess, and not familiar with the William's system.
In my Gottlieb games there is one plug board (10 positions, 1,000 to 10,000), and a set of 10 pins (10, 0 to 90,000) - you can plug multiple pins into different plugs for score combos, so my present settings on a Duotron (although not what's shown in photo):
53,000 = 50,000 pin into 3,000 plug
67,000 = 60,000 pin into 7,000 plug
75,000 = 70,000 pin into 5,000 plug
I was charmed when I realized this was how replay levels were set (and amused that it forces odd award levels, since you can only have one of each 10,000 place and one of each 1,000 place in the awards, rather than nice round numbers) - game designers were a creative bunch. Having lived with but not paid much attention to these oddball replay levels all my life it was cool realizing there was a reason behind them.
My older Domino has 10 plugs (100s digit), but fewer wires (1000s digit), and several of those have multiple daisy-chained pins so I can have multiple awards at the same 1000s score levels. And many of the 1000s wire markers were missing so I made some guesses and then trial and error'd things.