Often wondered about that. Obviously the heavy side of the rim should be were the valve stem is because thats the added weight, but is the rim itself balanced?The dot should line up with he heavy side of the rim, which is usually the valve stem, but not always. I had a yamaha vstar that both rims when balanced alone, was heavy 180 degrees opposite the valve stem. When I linedthe dot up on that side of the rim, the wheel was perfectly balanced and did not need any additional weight. Check the balance of the rim with out any weights on it. It might surprised you. Just my two cents.
When I mounted my Kenda's there was 3 white dots & one yellow dot. After contacting the seller, I found out the yellow dot was what you lined up with the valve stem. The white dots were false balancing marks made by the manufacturer.You could go to the manufacturer's website and maybe find out what the white dot indicates. As I understand it, yellow is the standard balance mark throughout the industry, including car tires.