Everyone who know the problem help me pls !

I want to refine from G to DG but it can't
already usable requirement skill lv, str, luck using G8
item +7 as require

http://postimg.org/image/5au39biaz/

http://postimg.org/image/hnftp5gmj/

http://postimg.org/image/k5o73zf57/