I don't know how to make Smelting system. i made some scripts, but it doesn't work the best

I have a problem with scripting. i want to make something like furnance, i made recipes for smelting, but i have problem with fuel system.

I tryed to made this, but program has problems with fuel counting.

link to program:   https://cdn.discordapp.com/attachments/612311027639517288/6888011185992…

link to image:  https://media.discordapp.net/attachments/612311027639517288/68880127536…

pliss help ;-;