n1

    (Length) is the maximum number of lines on a page; n1 cannot be
    smaller than 13.

 +n1

    Increases the current page length by n1 lines.

 -n1

    Decreases the current page length by n1 lines.

 n2

    (Width) is the maximum number of characters on a line for running
    heads; n2 cannot be larger than 150.

 +n2

    Increases the current page width by n2 characters.

 -n2

    Decreases the current page width by n2 characters.