It all depends upon who provided the information to the store, and how accurate it was. It is possible to have a late born hatchling from a second clutch. It is not the usual scenario, and I'd look at the age skeptically, not that it matters much. Some breeders feed hatchlings and young snakes a maintenance diet, just enough to keep them growing at a slow pace. It makes economic sense to them if they feed one pinky every 10 days and the corn subsists and makes slow growth. I've bought 2 year olds that weren't up to the size of my own yearlings, but they still matured properly.