I know it increases it one stage, but how much is "one stage"?
Accuracy = a 0: a +1: a x 1.33 +2: a x 1.66 +3: a x 2 +4: a x 2.33 +5: a x 2.66 +6: a x 3
Source: Experience and this.
Blizzard: 70*1.33=93.1->93 accuracy.