NBT Block Variables only working sometimes, and showing up as -1.0

I need some help with NBT Block variables. I am trying to make it so that a procedure puts an item in a slot of a GUI if an NBT variable is equal to 22. I made it so that whenever you push a button in the gui, it adds 1 to that variable. (Whenever the GUI is opened it automatically sets the variable to 0.) The thing is that the variable always shows up in the console as -1.0 if I print it. The really silly part of this is that I also have different images that show up inside of the Same GUI that are also depending on that same variable. The images show up and work every time. I have remade every single procedure linked to the GUI MULTIPLE times, but it still does not work. I can provide more detail on the triggers of the procedures if needed.