INCORRECT SUBTOTAL

Hi, 

I have some issues with adding up the sub total in the martix table. kindly advise. thank you
Formula used as per below: 

New Member Sales =
CALCULATE (
    SUMX (
        WTMembersTransactionsDetailsReport,
        WTMembersTransactionsDetailsReport[Nett]
    ),
    FILTER (
        WTCustomizedCardsListingReport,
        WTCustomizedCardsListingReport[Issue Date]
            > LASTDATE ( DateKey[Date] ) - 30
    )
)

New Member Sales Total =
IF (
    COUNTROWS ( VALUES ( DateKey[MonthNo] ) ) = 1,
    [New Member Sales],
    SUMX ( VALUES ( DateKey[MonthNo] ), [New Member Sales] )
)