The Refund option in shop?

There's this feature that has been bothering me for quite a while, and i don't know if it's a bug, or it's intentional. Has anyone noticed that when you return to base and buy something, and after you healed, then refunded it, that your hp undo's along with the item? I was thinking that you just undo the purchase, not the entire time you were regenerating health and mana at base.