The .RIGHT MARGIN command sets the right margin to the position
    that you specify. This is the position to which a line of text
    normally extends. If .JUSTIFY is in effect, the .RIGHT MARGIN
    value is the position against which text is justified. If .NO
    JUSTIFY is in effect, the .RIGHT MARGIN value specifies the
    maximum number of characters on any text line. (Compare with
    .PAGE SIZE, which sets the page width for running heads.)

    Format

      .RIGHT MARGIN  [[+/-]n]

    Abreviated format

      .RM  [[+/-]n]