If grouping by "Week Number" in Financial Reports, any Financial Lines will be included if they have a start date that falls in that week.
A Financial Line Date is e.g. the date an Object is booked or added to a Time Report or the date it was added as extra to a Project etc. It's also the Date a Budget Line was added.
A report grouped by "Week Number" could be used to break out a project's expected costs, hours, expenses or bookings by week, making it easier to manage staying on track for a project.
So if you have bookings that go over a week, the revenue/data will fall into the week group of where the start date of the booking is.
Using the "View Class Booking As Separate Days" option on all bookings (you can set as default on Server > Bookings tab) the amounts will be distributed across the several weeks.
However! Certain limitations apply if using FIXED PRICE on Booking > you must NOT USE the "View Class Booking As Separate Days" option as it will result in wrong totals.
Example with "View Class Booking As Separate Days" option = ON
Example with "View Class Booking As Separate Days" option = OFF