Rear Wheel Axel Depth Setting Question

I have an Argon18 E112. Just curious what is the optimum clearance between the tires leading edge and the wheel cutout. I can see trough the gap between the tire and the cutout. does the wheel need be closer in or not. I had a shop adjust/center the rear wheel and it appears now that the adjustment took the wheel axle further out and away from the cutout.
Thanks