Hello mate

right im not 100% on wich way the numbers work but that can be trial and error - i cant remember whether its 4 for the deepest cuts on the key or 1 for the deepest.

Done a few myself but the last one i did the key was soo warn i just played with the numbers till it worked.

basically you start at the end of the key, i think you stick a washer in first then a number, then you stick washers in between each number till you are at the top of the key followed by another washer.

i know its not great help but its all trial and error like that and you will get it.