First Time Fix Rate

HI king98027,

You can use the following measure formulas to get the fist time flag and rate:

First time Flag =
VAR currDate =
    MAX ( Table[Created Date] )
VAR last7dayCount =
    CALCULATE (
        COUNT ( Table[Work Order Number] ),
        FILTER (
            ALLSELECTED ( Table ),
            [Created Date] < currDate
                && [Created Date] >= currDate - 7
        ),
        VALUES ( Table[Serial Number] )
    )
RETURN
    IF ( last7dayCount > 1, 0, 1 )

first time rate =
VAR currSerialNumber =
    VALUES ( Table[Serial Number] )
VAR summary =
    SUMMARIZE (
        Table,
        [Serial Number],
        [Work Order Number],
        [Created Date],
        "Flag",
            VAR last7dayCount =
                COUNTX (
                    FILTER (
                        ALLSELECTED ( Table ),
                        [Serial Number] = EARLIER ( Table[Serial Number] )
                            && [Created Date] < EARLIER ( Table[Created Date] )
                            && [Created Date]
                                >= EARLIER ( Table[Created Date] ) - 7
                    ),
                    [Work Order Number]
                )
            RETURN
                IF ( last7dayCount > 1, 0, 1 )
    )
RETURN
    DIVIDE ( SUMX ( summary, [Flag] ), COUNTROWS ( summary ) )

Regards,

Xiaoxin Sheng