Quick question about subscription

Hello, just want to clarify one thing that I am not sure. Well, I'm currently using Norton Security Premium and I have 155 days left of subscription. Now, I recently found pretty nice deal for extend my subscription for another one year. And I want to make sure that once I'm logged into program and then click Help > Enter Product Key, Norton will automatically add new 365 days to the current status of my subscription and then I should be at 520 days? I know that I can always contact Symantec Support and they will transfer that, but I want to know if Norton can do this by itself? Can anyone done that this way and can confirm that?

Thanks in advance!