We make every effort to disclose non-trivial damage to the holders, but minor imperfections such as light surface wear or slight inner well scuffing (present at the time of encapsulation) are common straight from CGC/CBCS/PGX. Newton Rings are also extremely common in newly slabbed CGC books (CGC tried to better protect the books by sandwiching them tighter in the cases, but as a result, a very large portion of newly slabbed books have some degree of rings).
If these are important to you, please message and we'll be happy to provide more detail on the case. For those unfamiliar with Newton Rings: This is an occasional effect produced by the inner and outer cases being in direct contact with one another.
The visual effect is similar to oil on a water puddle because of the two plastics. Ultimately it is not anything that is in direct contact with your comic, nor will it affect the comic's condition over time.