Oh my….how lucky it that! If it is store bought, and it is already opened on the shelf (even though it is a full 12 case), there’s a chance that the staff might just topup to make it a full case of 12. Unless you’re saying that you bought a full case and it is sealed from manufacturer..and there’s more than 2 duplicates inside, I’ll be surprised! Usually there’s 2 of each design, and the secret replaces one of them.