Yes, exactly. If you want to cast one spell, you must spend one daily slot of same or superior power (so, for a common spell you can use any slot, for a master spell you must use a master or supreme slot, and so on); every day, assuming you had at least 8 hours of rest, you recover every spent slot.<br/><br/>(The only difference from mana is that you can't spend more low-power slots to one high-power spell)