Library /sys$common/syshlp/lse$clihelp.hlb ENLARGE, WINDOW, Parameter  *Conan The Librarian (sorry for the slow response - running on an old VAX)

 line-count
    Specifies the number of screen lines you want to add to the
    current window. If you do not supply this parameter, LSE prompts
    you for the number of lines to add.

    The maximum size of a window depends on the size and type of the
    terminal screen you are using. The minimum size is one line of
    text and one line for the status line.