Tectonic theory is ur answer
Density is related to weight and box measurements. Since the box is the same only factor changing the density of the box is the weight of what’s in it. Box with marbles has the greatest density
It could be because India Is one of the most populated places so 12 in India doesn't seem that much there but if those numbers of people came to a country with a lower population it would be a higher percentage. if that makes sense..