Talk:Ashe/Strategy/@comment-1679053-20130104044937/@comment-1088372-20130116013648

"Unique Passive - Mana Charge: Each time you attack, cast a spell or spend mana, your maximum mana increases by 4 (3 second cooldown). Bonus caps at +750 bonus mana."

But to answer OP: Because you both attack and spend mana, this mystiquely grants you 8 mana per shot, and makes the manamune go on cooldown. It's not known whether this was intended.