The main part of the schematic in your JPG relates to the match feature, not the scoring. But look along the top of what you pasted. You'll see switches labeled "9th Pos Hundreds" and "On Add Hundreds" for each of the 4 players. Switches are the little sets of two vertical lines. Open switches have just the two vertical lines. Closed switches have the two vertical lines, plus a diagonal line going between them. I visualize the schematic as having "power" in the left-most vertical line in your picture, and "ground" is the right-most vertical line. The curly "pigtail" things are coils (relays or solenoids).
The M relay is for scoring 100 points, the L relay is for 1000 points. You see the Hundreds Chime solenoid (at the very top left of your picture) gets energized when the M (100 pt) relay closes, because the switch labeled "M" (over toward the right) closes and completes the circuit. If you look elsewhere on the schematic, you can find the "Add 1st 100s Unit" solenoid (for example), which is the coil that advances the 100 pt score reel for player 1. You will see that that coil gets energized through another switch on the M relay, and also through one of the switches (like P1C) on the Player unit (which controls which player's score is getting bumped up).
The wires in between the switches and coils are all labeled (on the schematic) with a color code (like BL-WH for Blue with a White tracer, there should be a key on the schematic). So look, for example, at the "Add 1st 100s Unit" coil on the schematic. What are the colors on each side of that coil? The main "power" side of everything is typically black. The other side of the coil will be labeled on the schematic (let's suppose it is OR-RED). Then go look at the actual wires connected to the coil on the 1st player 100 point reel. If one wire is black and the other is OR-RED (orange with red tracer), then it is OK.
On each of the score reels, there is a "9th Position" switch that closes when that reel is showing "9". There is also a "Zero Position" (or "Reset") switch, and a "Runout" switch (closed when the reel is non-zero). In addition, there are two switches (labeled "On Add 1st Hundreds" etc.) - one normally open and one normally closed, that get closed (or opened) when the score reel coil pulls in and advances the reel. You can see each of these switches if you examine the score reel closely. You can also find those switches on the schematic and check the wire colors that should be attached to them.
Looking at your picture, you'll see that the "L" (1000 pt) relay gets energized when that switch on the M relay closes, IF the 9th position switch AND the "On Add Hundreds" switch for the current player are also closed. This is what adds 1000 points when the hundreds reel is at 900 (9th position) and you score 100 more points (closing the M relay and bumping the 100s reel "up" to zero). When the 100 pt score coil pulls in and advances itself, the "On Add Hundreds" switch (that is normally open) closes, thereby energizing the L relay and also advancing the 1000 reel.
I am no expert myself, but hopefully this helps a little.