Short answer: do whatever works for you and your team.
Longer answer: most people don’t bother with hours. The 7 days are to have a very loose timeframe to scope something small. Personally, I count as one day any day that the work I did feels like enough progress (and that usually ends up being around 5 hours of working on it), and I count as half a day any in which I just could spend a couple hours here and there.
For teams most participants go with 7 ‘sessions’ per person when working separately, and combine the days they work together.
The 7 is also pretty loose. We don’t care if it’s 5 or if it’s 10. Again, this is just to help you scope your project into something small and doable, not to restrict your creativity.
So in summary, do whatever works for you, whatever helps you make and finish your game.
Cheers!