trancemission

Hey guys I did a search on this and did not find out much info on this and I would like your opinion. What direction should drilled and slotted rotors turn. I always thought they were directional with rotation. My friend just got a set on his car and they were actaully labeled. I have seen them both ways. My buddy works up at D&M auto leasing and I went up there to see this lamborghini they just got in and its back rotors were on in one direction and front ones were on going in the other direction. That just confused me even more. I understand their purpose, but which direction should they rotate to be most effective? Thank you in advance for your time. Ethan