Minecraft wiki entry for Instant_Health, associated text: Instantly heals 2 × 2level. In the upcoming Combat Tests, it heals 3 × 2level. Undead mobs (including the wither) are damaged as if with Instant Damage, instead. When applied using a lingering potion, the entity is healed every second. Levels 30–32 (amplifiers 29–31) provide no healing. Levels outside the range 1–32 (corresponding to amplifiers 0–31) are used modulo 32, making level 33 the same as level 1, etc.