So i got my a8 rotors from ecs in the mail today i opened them up, looked them over, i like them as of now, but is this a defect or no?

The other one around the outside does not have something like this, and this one does

heres 2 pics:

 

I just dont want to mount them, then get vibration etc, and cant send them back cause i used them, so i want to know before i put them on so i can send them back ASAP if anything.

But if thats the case then im fine with it, especially since i got them on sale

 

Likely done to balance the rotor, won't affect performance at all. if you have a cone balancer you could check it.