Mariano,
I like to explain you our requirement .We like to calculate average daily requirement for 90 days..that's the reason we put 13 weeks. Our period is monthly but for dynamic calculation we like to use weekly.
We are using week indicator for calculation and work days for Type of Per. Length that is indicator 1.My understating is if you are using anything except standard days indicator 3 in the field type of per length the number of days per period should be 0.
I made changes as per recommendation and put 1 number of days per period.
MD04
We are using PD MRP type and monthly lot size. We don't have any rounding value.