Calculating Working hours

HI rocky09,

You can try to use below calculated column formula to calculate valid working hour:

Work Hour = 
VAR filtered =
    FILTER (
        ADDCOLUMNS (
            CROSSJOIN (
                CALENDAR ( [ACTIVITY_DATE], [LASTMODIFIEDDATE] ),
                SELECTCOLUMNS ( GENERATESERIES ( 9, 18 ), "Hour", [Value] )
            ),
            "Day of week", WEEKDAY ( [Date], 2 )
        ),
        [Day of week] < 6
            && [TicketID] = EARLIER ( Table1[TicketID] )
    )
VAR hourcount =
    COUNTROWS (
        FILTER (
            filtered,
            (
                [Date] >= DATEVALUE ( [ACTIVITY_DATE] )
                    && [Hour]
                        > HOUR ( [ACTIVITY_DATE] ) + 1
            )
                && (
                    [Date] <= DATEVALUE ( [LASTMODIFIEDDATE] )
                        && [Hour]
                            > HOUR ( [LASTMODIFIEDDATE] ) - 1
                )
        )
    )
VAR remained =
    DATEDIFF (
        TIMEVALUE ( [ACTIVITY_DATE] ),
        TIME ( HOUR ( [ACTIVITY_DATE] ) + 1, 0, 0 ),
        MINUTE
    )
        + DATEDIFF (
            TIME ( HOUR ( [LASTMODIFIEDDATE] ) - 1, 0, 0 ),
            TIMEVALUE ( [LASTMODIFIEDDATE] ),
            MINUTE
        )
RETURN
    IF ( hourcount <> BLANK (), (hourcount*60 + remained)/60, 0 )

Regards,

Xiaoxin Sheng