VMS Help DSR, DSR Commands, .SET LEVEL, Parameters  *Conan The Librarian (sorry for the slow response - running on an old VAX)

 n

    Specifies the level for the next .HEADER LEVEL command.

 +n

    Makes the level for the next .HEADER LEVEL command n more than
    the current level.

 -n

    Makes the level for the next .HEADER LEVEL command n less than
    the current level.