To add to this, the boy at 3 o'clock, whose head is split in two equal pieces, is the key to the sleight of hand.

Does his head stay or does it move?

If it moves, the boy at 2 o'clock should count as 2 heads in position B. If it stays, then he should count as 2 heads in position B, since the head below him moves up.

But because it's ambiguous, we count it as both moving and not moving.