Grouped Average

I have a little rule that says if you have the option of doing it in TSQL before you get to Power BI then thats usually better since the model will be faster but assuming you cant do that:

so you've mentioned a COUNT a SUM and an AVERAGE but It looks like you just use Average - is that like a daily average? so in the first column you had on average 31.3 items overdue each day?

You could just build one measure the calculates "Daily Average"

Something like

Overdue Items = COUNTROW(Table)

Days = DISTINCTCOUNT(Table[Date])  -- note but be a date not a datetime

Daily Average = DIVIDE([Count of Overdue],[Days],0)

Then you put that measure in Values, Week_End in the Axis, Group in the Legend.

for each Week and Group it will determine how many items divided by how many distinct days??

is that what you are after?