I can't really tell from your pic, but what kind of mark is it? Is it a smudge, a stain? Does it have an identifiable smell? It could be a simple matter of wear and tear of the cupsole vulcanizing mold, in which case all CPs using that sole will have that flaw from here on in, until the mold is replaced, which could be years, decades even. Though this is probably not much comfort to you, flaws of this sort are likely to be COMPANYWIDE (or at least model-wide) and are not likely to get rectified, at least not during the current grey suede season.
Is there a discoloration? That could be caused by any number of things, most often contact with lower quality tissue paper - the acid in the paper reacts with the vulcanized rubber, causing a stain, which penetrates deeper the longer the shoes are (improperly) stored in this manner. In extreme cases, this can even cause cracking, which is why I never by shoes older than 2009, and NEVER buy deadstock shoes from manufacturers with KNOWN storage tissue issues (Raf... I'm looking at you, here).
Need better pics and a more detailed description to make a proper assessment.
Yours in fashion - CA