For unrolled activites such as DV, Mental DV, or feats of strength, Charms increase a character's static rating by adding to (the relevent Attribute + Ability). This bonus increases the (Attribute + Ability) pool, not the final result of any calculations, so if the (Attribute + Ability) is divided in half, the bonus rating will be applied before the division, not afterward. The result is that player will normally have to add two "dice" to increase a static value by one - although the First Excellency provides a discount of sorts for this, increasing static values by one per success rolled.
Regardless, no combination of Charms, including the First Excellency, can increase a static rating by more than half the (Attribute + Ability), and Charms that remove penalties do not count as increasing the character's static rating.