How does spellburn healing work with several ability scores

In DCC RPG, a Wizard may sacrifice some points of Strength, Agility or Stamina to give a one-time bonus on a spell check. These points of ability scores are not gone permanently, but can be healed.

Ability scores lost in this way return as the wizard heals. Each day he does not attempt spellburn, he recovers 1 point of ability score.

(Emphasis mine.)

My question is what does this “1 point of ability score mean”? One point in total, only increasing one of the three ability scores which it is possible to heal, or one point per ability score which has been depleted? I can’t find any further clarification in the book.