Formula to Calculate Usage

Hi, hamzashafiq 

You can calculated columns as below:

YearMonth = DATE('Table'[Year],'Table'[Month],1) 

Start_date = 
CALCULATE (
    MAX ( 'Table'[YearMonth] ),
    FILTER (
        'Table',
        'Table'[Max Hours] <> BLANK ()
            && 'Table'[YearMonth] <= EARLIER ( 'Table'[YearMonth] )
            && 'Table'[Serial Number] = EARLIER ( 'Table'[Serial Number] )
    )
)

Diff = 
VAR MaxHours =
    IF (
        'Table'[Max Hours] <> BLANK (),
        CALCULATE (
            MIN ( 'Table'[Max Hours] ),
            FILTER (
                'Table',
                'Table'[Serial Number] = EARLIER ( 'Table'[Serial Number] )
                    && 'Table'[Max Hours] > EARLIER ( 'Table'[Max Hours] )
            )
        ),
        BLANK ()
    )
VAR MinHours = 'Table'[Max Hours]
RETURN
    IF ( MaxHours = BLANK (), BLANK (), MaxHours - MinHours )

Usage = 
VAR Max_hours =
    LOOKUPVALUE (
        'Table'[Diff],
        'Table'[Serial Number], 'Table'[Serial Number],
        'Table'[YearMonth], 'Table'[Start_date]
    )
VAR Count_month =
    CALCULATE (
        COUNT ( 'Table'[Start_date] ),
        ALLEXCEPT ( 'Table', 'Table'[Serial Number], 'Table'[Start_date] )
    )
RETURN
    Max_hours / Count_month

Best Regards,
Community Support Team _ Eason
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Hi, hamzashafiq 

I may have misunderstood what you meant before. From your last screenshot, the value of some months (3,4,5,6,7,11,12) is missing rather than 'blank'. If so, please check my new attachment. Hope this could help.

Best Regards,
Community Support Team _ Eason