Well, people put these traffic light things on food labels to make it easy for people that cannot think to see if something is good or bad for them!
But the labels are "per portion", so of course producers just make smaller recommended portions if their produce looks bad.
A 150g pack of crisps is labeled for 1/6th of a pack portions.
But its not like it is practical to re-seal it... I'll end up eating it all.