You gain a +2 bonus to AC against ranged attacks while you wield this shield. This bonus is in addition to the shield’s normal bonus to AC. In addition, whenever an attacker makes a ranged attack against a target within 5 feet of you, you can use your reaction to become the target of the attack instead.
RollQuest ships the D&D 2014 SRD as a content pack, on a 5e character sheet that does the maths - roll from the sheet and let the numbers work themselves out. Free to start.