VMS Help DSR, DSR Commands, .DISPLAY LEVELS, Parameter  *Conan The Librarian (sorry for the slow response - running on an old VAX)

 y

    One of the following one- or two-letter codes; 1,2, ... 6
    indicate positions of numbers (or letters) for a section header.
    The commas correspond to the dots in a printed section number.
    (See also .NUMBER LEVEL.)

    Code  Form of Sequence and Case

    D     Decimal numbers
    O     Octal numbers
    H     Hexadecimal numbers
    RU    Roman uppercase numerals
    RL    Roman lowercase numerals
    RM    Roman mixed case numerals - only first numeral is uppercase
    LU    Letters, uppercase
    LL    Letters, lowercase
    LM    Letters, mixed case - only first letter is uppercase