What error?

I want ask yours opinion - if I clocking ball rotations say in 4 sec ball do 3 rotations and dropping point is at 9 oclock. Next time I get the same result - what diference in dropping point can be ?

If I understood you right, you are asking what would be difference in between 2 identical spins at some particular moment when they make 3 rotations in 4 sec.

Assuming that your measurement is accurate you may get very similar result but it can be different. In usual with that ball speed range it will stay within ΒΌ-1/3 of rotation if the wheel is good and leveled.
If it is with dominant drop point it will most likely have same result, or perhaps some spins may go for additional rotation.