help with taking items

[shadow bay]

on right click: if player's tool is not air: if name of player's tool is "&6Infernal Core": delete player's held item

the type of item is a player skull. the user who owns this skull is SlianKobold (i dont think thats important)

Basically, the skript works fine except if i have multiple, it deletes them all. i only want ti to take away one. By the way its a custom entity skull (the texture for the infernal core) So i just need help to figure out how to just remove 1

[rigid dagger]

1. line 2 is useless, as line 3 checks the name. Air cannot have a name
2. set the item amount of the player's tool to itself - 1

[shadow bay]

i fixed issue 1. how would i do issue 2