DAX Help

AV_04 , Okay then please create a column as below:-

_no_stocks_left = 
VAR cust_bought =
    COUNTROWS (
        FILTER (
            'Table',
            'Table'[Product] = EARLIER ( 'Table'[Product] )
                && 'Table'[Sub-Product] = EARLIER ( 'Table'[Sub-Product] )
        )
    )
VAR stock_available =
    CALCULATE (
        MAX ( 'Table'[Stocks Available] ),
        FILTER (
            'Table',
            'Table'[Product] = EARLIER ( 'Table'[Product] )
                && 'Table'[Sub-Product] = EARLIER ( 'Table'[Sub-Product] )
        )
    )
VAR _result = stock_available - cust_bought
RETURN
    IF ( _result = 0, 1,0 )

Then create a measure as below:-

Measure = 
CALCULATE(DISTINCTCOUNT('Table'[Sub-Product]),FILTER('Table','Table'[_no_stocks_left] = 1))

Refer a file below:-