Example code for this can be found in UpdateManager.py:


    def matchPackageOrigin(self, pkg, matcher):
        """ match 'pkg' origin against 'matcher', take versions between
            installedVersion and candidateVersion into account too
            Useful if installed pkg A v1.0 is available in both
            -updates (as v1.2) and -security (v1.1). we want to display
            it as a security update then
        """
        inst_ver = pkg._pkg.CurrentVer
        cand_ver = self._depcache.GetCandidateVer(pkg._pkg)
        # init with empty match
        update_origin = matcher[(None,None)]
        for ver in pkg._pkg.VersionList:
            # discard is < than installed ver
            if (inst_ver and
                apt_pkg.VersionCompare(ver.VerStr, inst_ver.VerStr) <= 0):
                #print "skipping '%s' " % ver.VerStr
                continue
            # check if we have a match
            for(verFileIter,index) in ver.FileList:
                if matcher.has_key((verFileIter.Archive, verFileIter.Origin)):
                    indexfile = pkg._list.FindIndex(verFileIter)
                    if indexfile: # and indexfile.IsTrusted:
                        match = matcher[verFileIter.Archive, verFileIter.Origin]
                        if match.importance > update_origin.importance:
                            update_origin = match
        return update_origin

    self.matcher = self.initMatcher(dist)

  def initMatcher(self, dist):
      # (origin, archive, description, importance)
      matcher_templates = [
          ("%s-security" % dist, "Ubuntu", _("Important security updates"),10),
          ("%s-updates" % dist, "Ubuntu", _("Recommended updates"), 9),
          ("%s-proposed" % dist, "Ubuntu", _("Proposed updates"), 8),
          ("%s-backports" % dist, "Ubuntu", _("Backports"), 7),
          (dist, "Ubuntu", _("Distribution updates"), 6)
      ]
      matcher = {}
      for (origin, archive, desc, importance) in matcher_templates:
          matcher[(origin, archive)] = self.UpdateOrigin(desc, importance)
      matcher[(None,None)] = self.UpdateOrigin(_("Other updates"), -1)
      return matcher

Thanks,

James

This is already fixed in 0.3.0. 

I adapted and pushed the code which reports updates as security updates if they succeed one some minutes ago.