A Mutable Item Stack is a special IItemStack object that can only be retrieved from ICTPlayers.
That means all of IItemStack's methods, and those of IIngredients!

It might be required for you to import the package if you encounter any issues, so better be safe than sorry and add the import.
import mods.contenttweaker.MutableItemStack;

A Stack's count is the number of items in that stack!

ZenMethod	参数类型	描述
ZenMethod setCount(count)	参数类型 int	描述 Sets the stack's count to the count provided
ZenMethod grow(count)	参数类型 int	描述 Increases the stack's count by the count provided
ZenMethod shrink(count)	参数类型 int	描述 Decreases the stack's count by the count provided

damage(int amount, ICTPlayer player)

Parameters:

• int amount → The amount of Damage points to give the item
• ICTPlayer player → the player/Entity damaging the item