Remaining subscription days not added to new key/subscription

I type in my new Norton Security product key to renew my Norton Internet Security that has 21 days left, because I see that the 21 days will be added to the new 1-year subscription:

Norton_Renew.JPG

But after it activate with the new key, I see that I only have 366 days remaining instead of 365+21 days:

Norton_Post_Renew.JPG


What's going on? Did I just lose 3 weeks of subscription?