Hi. O.K. I understood about my problem. And now we aren't using gradebook_cdc. I think it is difficult to use it soon, because there is not Japanese lang-pack and it is not in official distributiion. I will try in future.
But now, I'm expecting simple highscore block for one quiz activity.
And, I expet a optional setting for quiz module:
When students get quiz score result , they can know their ranking position and best 10 scores.
(I should ask about this in Quiz forum...)