Although there is only a 10% chance to save an ingredient, the scroll saves on average 1/9 of ingredients when re-using the saved ingredients. This is because each saved ingredient also has a 10% chance of being saved again. For example, if 1,000 ingredients are used, 100 should be saved because of the scroll. However, the 100 saved ingredients also have a 10% chance of being saved, so after using them there would be 10 more. Likewise, on average 1 of the 10 ingredients saved from the 100 would be saved. This adds up to an expected 11 % rate of herb saving when the savings are compounded. For example, if you wanted to create 1,000 potions, you would normally need 1000 herbs or 1000 secondary ingredients. However, with the scroll of cleansing, you only need 900 herbs or 900 secondary ingred