What are those tiny circular "scratches" on DVD-R? (PHOTO !)

[Khizhiy]

I've noticed a tiny circular "scratch" right at the beginning of the writable area of a DVD-R and DVD-RW (close to the center of the disk). Does anyone know what this is? It is not really a scratch; it is under the upper protective layer, but it can be easily seen.

[Khizhiy]

Okay, so no one knows what this is. Then, tell me please if you saw the same phenomena on your DVD-R(W)'s. Look at the picture for reference:

I wonder if this is a defective or normal DVD-RW.