Not understanding the logic of Discovery's Healthy food points

I have asked Discovery Vitality the following question about their Healthy Food points but only got a standard response that did not answer my question: if I buy a box of milk containing 6 x free fat 1 liter boxes I M credited with 1 point for healthy food. If I buy these separately I get six points. The same apply to unhealthy food points. If I buy 1 kit kat I get 1 point againt me, and if I buy one pack of 12 double kit kats I still only get 1 point deducted? Can you explain this please? Do you force me to pay extra to buy single boxes of milk?