EARLIER Function

Since the introduction of VAR, there's no actual need for EARLIER any longer.  So you might want to do it in a different way, perhaps easier to follow conceptually, and forget about EARLIER altogether (which is actually recommended nowadays):

Value2 =
SWITCH (
    TRUE (),
    Table1[GroupOrder] IN { 1, 4, 7 }, 0,
    Table1[GroupOrder] IN { 2, 5, 8 },
    VAR PreviousGroupOrder_ = Table1[GroupOrder] - 1
    RETURN
        CALCULATE (
            DISTINCT ( Table1[Value 1] ),
            Table1[GroupOrder] = PreviousGroupOrder_,
            ALLEXCEPT ( Table1, Table1[Date] )
        ),
    Table1[GroupOrder] IN { 3, 6, 9 },
    VAR PreviousGroupOrder2_ = Table1[GroupOrder] - 2
    RETURN
        CALCULATE (
            DISTINCT ( Table1[Value 1] ),
            Table1[GroupOrder] = PreviousGroupOrder2_,
            ALLEXCEPT ( Table1, Table1[Date] )
        )
)