Minecraft wiki entry for Cauldron, associated text: Using an arrow on a cauldron that contains a potion transforms the arrow into a tipped arrow with that potion effect, and reduce the potion in the cauldron by one level. Tipping multiple arrows at once can be more efficient, and it may use more than one level at once. 1 level of potion tips up to 16 arrows, 2 levels up to 32, and a full cauldron can tip a full stack of arrows, resulting in 21.33 tipped arrows per potion.