When you craft something on the crafting table it shows you what you are making in the square next to the 9 crafting squares. then if you take a bundle, pick up everything from the 9 squares, that one square stays and you basically duplicate anything. example - when crafting a block you pick up the 9 ingots with the bundle and then the block - you start with 9 ingots and end up with 18, you can do it as many times as you want and it still works. you can do it with anything thats craftable