Ended my call
The guy came back and stated the promo "might" not be able to registry until Jan 7, the day when the promo will start. I question him about the Delta ad. He called his manager and got a respond that the ad is incorrect.. and will try to get it adjust as soon as possible. (sorry to all if it is me who screw up the chance to move the start date back to Jan 1)
so, it look like any discrepancy info on the Delta ad are error (like the typo others had posted above) and we "might" need to wait until Jan 7 to registry before we check-in as stated in the T&C.
alc