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

       /NUM_UNITS=number-of-units

    Specifies the number of units to be created. The starting device
    number is the number specified in the device name parameter.
    For example, the first device in DKA0 is 0. Subsequent devices
    are numbered sequentially. The default is 1. This qualifier is
    optional.