7 days - when does it start to count?

Hi,
I bought a JR Pass and I key in the travel date as 22-Nov-2014.
As I bought the 7 days pass, it'll expire on 28-Nov-2014.

Question is how does the 7 days being calculated?
Does it starts strictly from the day I key in, for my case 22-Nov-2014 or from the day I start the 1st travel?

I'm worried that I have made a mistake in the key-in date as actually, I need to use Sinkanshen on 27-Nov and 29-Nov.
if I go by the 7 days per my key in date, then I can't use the pass on 29-Nov anymore.

Pls help to advise.