When a title is issued in multiple series, BIBFRAME does not have a way to associate each series with its numbering.  For example, looking at OCLC #45898, as converted by the LC program, we find the following.

BIBFRAME Work

    bf:hasSeries <http://lib.washington.edu/ld/test/99130299090001452#Work830-36>,

        <http://lib.washington.edu/ld/test/99130299090001452#Work830-37> ;

    bf:seriesEnumeration "43",

        "7902" ;

BIBFRAME Instance

    bf:seriesEnumeration "43",

        "7902." ;

    bf:seriesStatement "African series",

        "Department of State publication" ;

In neither the Work nor the Instance can enumeration be associated with its series for the purpose of search or display.  This is a significant step back from current practice.