Welcome to the forum
Don't stress it dude. It's just a shim for the locking nuts.
You probably won't need it... For the most part, small adjustments or minor changes in the wood caused by temperature or humidity can be fixed with a quick set up and turn of the truss rod - So you shouldn't need to worry about it
But... if you wish to tweak things in the future you can use shims to raise or lower the overall string hight at the headstock end. I used my shim when I replaced a 15 year old floyd rose unit recently. Haven't need it before then
Once again, welcome... Now post some pics of your guitar!!!![]()