Calculate cumulative average by month

Hi all,

I want to calculate the cumulative average by month based on the selected year.


As you can see, I am able to get the desired output for year 2017. However, I cannot seem to get the correct output for year 2018, as shown below:



The cumulative average for January 2018 should be 37611 but it is showing 3134.25.

This is my formula:

SL06 cumTot = TOTALYTD(SUM(SL0006[Total]),'Calendar Table'[Date])

SL06 cumAvg = [SL06 cumTot] / CALCULATE(DISTINCTCOUNT('Calendar Table'[Month]),
    DATESINPERIOD('Calendar Table'[Date], LASTDATE('Calendar Table'[Date]), -12, MONTH))

Can someone please help me on this issue?

Thanks in advance.