Changing score by choice not possible on Multiple choices or drag and drop question slides

Hi,
I'm not able to have a logical result percentage after many tests, so I need your help.

My perfect score would be for :

- multiple choices slide : +1 when right choice, -1 when wrong choice or empty choice

- Drag-and-drop slide : +1 when right drag-and-drop, -1 placed at the wrong place

- One choice slide : +1 when right choice, 0 when wrong.

But the percentage shouldn't be under 0.

Can you please help me ?

Thanks,
Christelle