MOST (but not necessarily ALL) scopes are marked in the direction you want to move the point of impact. In your example, if the bullets are striking 3" to the right, you must move the adjustments 3 inches in the direction marked "left".

I know of no currently made sciope that is marked differently. But ages ago, some of the German scopes (IF they even had internal windage adjustments) were marked in the reverse of this - it made for some confusion!!