VMS Help CMS, DELETE, GENERATION, Qualifiers, /TO[=generation-expression]  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    Specifies the end of a range of generations that are to be
    deleted, including the specified generation. You cannot specify
    both /TO and /BEFORE or both /TO and /GENERATION. You must specify
    the start of the range with either the /AFTER or /FROM qualifier.