Its purly business call. In this scenario we cant define exactly what is the weekly hours because the 1st and 2nd week has different weekly hours.
You can check with your client and see whether you have any specific requirement based on this weekly working hours or monthly working hours.
For an example,If there is any requirement that you need to fetch the over time based on weekly working hours and also monthly working hours in IT0007 will be defaulted in IT0008, this will be used as dividing parameter for factoring andover time rate calculation in payroll.
So consider this 2 things and assign the value according to the requirement if you cant not assign the actual value.