You may want to mention to your local tire specialist that you would prefer to have the weights added to the wheel one at a time. Meaning: spin the wheel add the weight to the outer edge, spin the wheel again then add that the weight to the inner edge.

I have discovered a difference with two minor things, 1) up to 3 grams off and 2) the placement/location of the weight.

I found this method to work the best for Goodyear tires.