Yeah the size of the boy half goes from say 5% to 95% around the circle, on both sides. In the 12 boys configuration the halves are paired correctly to add up

Yeah the size of the boy half goes from say 5% to 95% around the circle, on both sides. In the 12 boys configuration the halves are paired correctly to add up to 100% sized boys. But in the other, there are 12 boys smaller than 100%, and then at 8 o'clock two 95% pieces appear together so we round them up to two. Neat illusion.