How do I make a self evident quantity selection?

When I showed the form to others they could not understand both clicking a check box and editing a drop down menu or changing a 0 manually to some other number. Is there a way to have a drop down menu starting at zero without a box to check so that it would be one click. 

Putting a value into the quantity box and/or selecting a quantity in the dropdown (for dropdown option) would automatically check the product item. 

Now, adding zero in the Dropdown Quantity option is possible. Just please check the "Add Quantity Property" without checking the "Custom Quantity" box.

Now, just simply add the zero at the beginning of the option:

Thanks