The text for this green item reads: “After you spend your Ultimate Charge, gain 25 Armor and 10% Ability Power for the rest of the round.”
When I tested this in the practice range, the +25 armor applied only one time, no matter how many times I ulted. If this item was intentionally designed to activate only once per round, it should say (max 1 use) in the item description.
a friend of mine thought the same as you. it is implied that it does not do it more in my eyes. but you are right. it only applies both buffs once.