FIRST value-expr

    Specifies how many records are in the record stream formed by
    the record selection expression (RSE). The value expression,
    value-expr, is a symbol or string of symbols used to calculate
    a value. The value expression in a FIRST clause must either
    be a positive number or a value expression that evaluates to a
    positive integer. The record stream cannot contain more records
    than the number specified by the value expression.