Kitchen paper towels dispenser box

The very quick and simple design of paper towel dispenser.

The purpose of that freehand "zigzag " hole in door is to see how much towels are left inside. The first idea was print filling for that with some transparent material, but I have no idea what's wrong with my Cura settings, when I set 100% filling, printer does not print exactly nice 100% transparent, but it keep some crossing pattern filling with tiny gaps and that was far from transparent.
Then I change setting to 0%, but it still