Board Thread:General Discussion/@comment-33554559-20180331013226/@comment-32271305-20180331015418

Well, that 10% is divided equally in featured SSRs and non-featured SSRs (5% each), and sadly 255 stones aren't enough for the law of large numbers to "guarantee" one SSR per multi-summon. Good luck with your future summons, though. I know it can be frustrating, I've also been very unlucky lately.