Hi,
You should use PlayerPrefs for this. This has an added benefit of being completly separated from potential value reset amongst level loading, AND you can keep track of that if the player quits and restarts the game.
But with your GameData Editor, don't you have this built in already?
The trick usually that I apply for this, is to create a "singleton" that I set to persists across level loading ( "Don't destroy on load" action ), and then if you load a level, the variables values will not be reseted and your score logic can rely on what will be available on that object.
Does that make sense?
Bye,
Jean