You only claim fate on a ring when you declare the attack. If there is fate on a ring on a province it stays there until it is able to be picked when you declare an attack from your unclaimed ring pool.
Ex: opponent has 3 fate on ring of water in his province. You bake the province and move the ring to one of your provinces with the 3 fate still on it. If you had the water ring already claimed it would go back to the unclaimed ring pool with the fate on it until the opponent declared a water attack .