By referring to them as "job specific" ones, they just mean it refers to the job leveling group of "Tales of Adventurer" items, as opposed to the story jump ones ("Tales of Adventure: A Realm Reborn" and "Tales of Adventure: Heavensward"). It's possible to buy both one level jump potion and one story jump potion, but not to get more than one from either of those categories. So yes, as Ellia said, it's limited to one job for one character.