I am suppose to figure out why and how this Magic Circle works.

I have 4 large circles with 6 smaller circles marking each intersection point. Different numbers in the small circles add up to 39.

I labeled my circles by colors such as:

Red circle: 3+5+6+7+8+10 = 39

Blue circle: 1+2+3+10+11+12 = 39

Orange circle: 1+4+5+8+9+12 = 39

Green circle: 2+4+6+7+9+11 = 39

How to I explain why and how this is true?

t-lee