If I understand you correctly you would want to have a snippet with a total line at the bottom of the page, such as:
Total: 8 8 8 8 8 0 0 0
I also understand that you're creating a non persistent entity (NPE) with attributes for the seven daily totals. Maybe you should add an entity week.
Associate the entity week to projecthours and to your totals NPE.
the snippet can then be filled by a datasource microflow that would have the week as input parameter and the user if you cannot use current user.
Now you can count the HourRegistrations for the week of this user….
If you make the NPE persistable, you can update the totals everytime hours are booked to a date….
Go make it!
Jacob