Date range slicer

Hi, 

I would like to know if a slicer visual for a date range will automatically configure the measures and calculate the sums and averages for the selected period on all visuals on the dashboard. 

I have created a date table and used this as my value for the slicer - I am using the 'between' slicer. The date table used for the slicer has an active realtionships with other tables as many to one, single.  

My question is the date slicer works absolutely fine if I am selecting a specific date, bringing all averages and sums correctly, but when I use a period date range, e.g. 15/03/20 to 20/03/20, my measures are not averaging right but all the sums are bringing the correct figure on my dashboard. 

Is there anything I am missing?

Thank you