Library /sys$common/syshlp/sysmanhelp.hlb SHUTDOWN, NODE, Qualifiers, /MINUTES_TO_SHUTDOWN  *Conan The Librarian (sorry for the slow response - running on an old VAX)

       /MINUTES_TO_SHUTDOWN=number

    The number of minutes until shutdown occurs. If the system
    logical name SHUTDOWN$MINIMUM_MINUTES is defined, its integer
    value is the minimum value that you can enter. Therefore, if
    the logical name is defined as 10, you must specify at least 10
    minutes to final shutdown or an error message displays. If the
    logical name is not defined, and you do not enter a value, 0
    minutes is the default.