If all Notches are being used, the Overcharmed cannot be activated. While in this state, the damage from all sources is doubled. The Overcharmed status is activated if there are more charms equipped than the number of Notches can support. Picking up a Charm Notch fully restores the Knight's health.
Different charms require a different amount of notches. Charm Notches are required to equip Charms.