The SparcII has a 2 MOA dot meaning it covers about 2" at 100 yards. I'd say an average shooter with the proper adjustment of the focus and a good cheek weld is going to shoot a 4-6" group with that at 100 yards, so don't get too worried. With practice, you should be able to get that to 2" or less with good ammo.

However, you did not mention what ammo you are shooting. I have some factory ammo that groups about 4" with a 10x optic, but I shoot my 69 Noslers from the same gun and the 5 shot groups are under 1/2" (100 yards).