The plan here is something along the lines of a "make it permanent" button. Otherwise, the process of correcting a mistake in the number of arrows you fired becomes a real hassle if you have to re-buy those arrows. Also, for cases like throwing daggers, where you have to collect them after the battle, having the option to not permanently remove them when they're used is important - during the battle, you need to know how many you still have left to throw, but after the battle, you'll usually get them all back.