Quick question about mast track settings. What are they and how should they be used?

What are they? Just reference marks, the numbers mean nothing, IMO.
Different conditions, and different sail sizes, but to a lesser extent, require different mast placements. Experimenting is the only way you can find your own sweet spot, which also depends on the individual, your height and weight, and how they effect the planning characteristics of that board. Make your own marks if you want.

Just guessing, but they may be the distance in centimeters from the centre of the base base to the centre of the fin box.

I vary the position of my mast base depending on a number of variables:
- potential board speed (fast - back, slow - forward)
- size of chop (flat water - back, choppy water - forward)
- type of fin (weed speed - back, pointer - centre to forward)

OK, well my general rule is for the first time on a new board put it in the middle, best starting point. Now this is going to vary a lot depending on rider weight, sail size and type and fin size and type, strap positions and boom height so lots of variables to get aligned for the perfect trim. Generally running the track forward is going to help hold the nose down and the board to trim flatter and it will track upwind better. However as it is triming flatter more surface area is in contact with the water and it may feel "sticky" If the board feels slugish and sticky try moving it back. Having the mast foot back will induce the board to ride more on it's tail. It will feel livelier and faster but you may have control problems when it gets windy and the board will tailwalk. If that is the case try it further forward.
I try to keep the mast base close to the middle and play with the other variables first, if I still can't get the board to feel balanced then I will play with the foot position.

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John340 said..
Just guessing, but they may be the distance in centimeters from the centre of the base base to the centre of the fin box.

I vary the position of my mast base depending on a number of variables:
- potential board speed (fast - back, slow - forward)
- size of chop (flat water - back, choppy water - forward)
- type of fin (weed speed - back, pointer - centre to forward)

You forgot...
- In the mood for catapaults - back
- still recovering from previous catapaults - forward