In this old thread in the Beta-forums, the questions was asked:
Does it apply to a shot where the total modifier is positive? For example, making a single shot (+10) at long range (-10) after having aimed for a half action (+10)? There are penalties, but they're outweighed by the bonuses.
Was this ever addressed?
Will this piece of gear do nothing when firing a full-auto weapon (-10) on Short Range (+10), but suddenly kick in at Normal range, when the total penalty to the shot exceeds 0?
As the wording says "all penalties" I am inclined to say that as long as there are any penalites in the equation, whether from range or firing mode, they are reduced before calculating the net total. Otherwise it becomes kinda strange, where the Targeter only "works" sometimes, depending on other circumstances.