Marriott has a bit of history with this kind of mix up. A few years ago when they first brought out the Premier Visa Card, they flubbed the 15 nights and accidentally gave everyone who had the card many more nights. And for a while, there were a whole lot of Plat members running around.

Once they fixed that little "error", they put everyone back to the elite level they were supposed to be at. They didn't let those affected keep their new found status.