I don't shoot mathews bows, but I recall that they recommend a starting position of aroung 13/16" (I think) from the riser to the center of your arrow on the rest.

That being said, You should notice that your string doesn't run exactly center of the riser -- it comes from the side of the bottom cam, so it is a little to the left (right handed bow) of the stabilizer hole.

Another thing is that with a short 34" axle to axle length, the cable roller gaurd is inducing a good bit of inherent torque into the system that increases with the draw cycle -- this tends to put the rest slightly a bit more left. This is also the reason that most people end up with there pins a bit to the left of the string at rest (but if they check them at full draw they will see they are indeed in line).

After all that rambling, if it seems way left, you might want to check it out. I put very little faith in paper tuning as you can easily get superfilous results. I shoot magnocks and can crank my Pro-tuner rest 10 clicks to the left and still get a bullet hole, just like when it is set correctly. Since you have a biscuit rest, powder testing to see which side of the rest is riding heavier can't be done, but you can still do a walk-back check by using the same pin and aim at the same spot and keep walking back and shooting until you run out of room on the target butt -- you should get a straight vertical line with your arrows, if the line progressively goes to one side as you go back, your centershot is probably off. This will get you in the ball park.