Returning Users Month over Month

Hi, I’m creating some numbers around the People who view our PowerBi Reports. More specifically I am calculating numbers for report viewers who come back month over month.

I’ve been able to generate the correct DAX to calculate People who return each month. But I’m not able to revise the calculation to get the Average number of returning people?

Attached is a PBX with an easy sample dataset along with the DAX i wrote for returning viewers. Any help would be appreciated here…
eDNA Returning Viewers.pbix (130.4 KB)
Returning Report Viewers.xlsx (17.7 KB)

*Returning Viewers =

VAR Unique_Users_Currnet_Period =
VALUES(‘Report Viewers’[Viewer]))

VAR Unique_Users_Prior_Month =
VALUES(‘Report Viewers’[Viewer]),
DATEADD(‘Master Date Table’[Date], -1,MONTH))