Aggregate average measure for calculating average ...

I have a measure like this

_DIFOT_MTD_Customer = 
    DIVIDE(
        CALCULATE(
            SUM('Annual Performance Keep Channel'[Value]),
            'Annual Performance Keep Channel'[Metric ID] = "52"
        ),
        CALCULATE(
            SUM('Annual Performance Keep Channel'[Value]),
            'Annual Performance Keep Channel'[Metric ID] = "37"
        )
    )

This is the formula when I want to calculate YTD value instead of MTD value

DIFOT ex NZ Customer MTD & YDT = IF(SELECTEDVALUE('YTD/MTD Selection'[YTD_MTD_Option]) = "MTD", [_DIFOT_MTD_Customer], CALCULATE([_DIFOT_MTD_Customer],DATESYTD(Dates[Date],"31/7")))

I expected that Power BI will calculate the MTD performance value of DIFOT, and then take the average. But what it did was take the sum of numerator and then divide the sum of the denominator, which will lead to a weighted average result.

Could anyone suggest me a way to fix this? Thank you so much