Custom column index

Anonymous 

Try this, with a minor change on how the ties are broken. It uses the Index column, which we didn't have at the beginning but is very useful. Seems to match the expected results on your uploaded  sample:

Attempt V2 =
VAR breakTies_ =
    RANKX (
        CALCULATETABLE (
            Table1,
            ALLEXCEPT ( Table1, Table1[Site], Table1[Operation] ),
            Table1[Time Stamp] = EARLIER ( Table1[Time Stamp] ),
            RIGHT ( Table1[Step], 3 ) = "001"
        ),
        Table1[Index]
    ) - 1
RETURN
    CALCULATE (
        COUNT ( Table1[Step] ),
        ALLEXCEPT ( Table1, Table1[Site], Table1[Operation] ),
        RIGHT ( Table1[Step], 3 ) = "001",
        Table1[Time Stamp] <= EARLIER ( Table1[Time Stamp] )
    ) - breakTies_

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