n

    Specifies the character position of the new right margin; n must
    be greater than the value for the left margin. (For example,
    .RIGHT MARGIN 60 sets the right margin just to the right of the
    60th character position.) The maximum value of n is 150.

 +n

    Sets the right margin n character positions to the right of the
    current right margin.

 -n

    Sets the right margin n character positions to the left of the
    current right margin.