Almost any silver or gold badge results in getting a bronze badge before it (in the middle of the way). For example, a question with 20 up-votes get the nice question silver badge, which means that when it's got to 10 up-votes, it's given the good question bronze badge.
Why this person (the image) in spite of having 92 silver badge and 13 gold badge, only has 21 bronze badge? Is this a bug? What is the explanation behind it?