I'm at somewhere in the 1800 scroll range right now (not 100% sure because I stopped counting the free pulls), but I've done 5 300 pulls, 2 100 pulls, and a bunch of random 10 pulls.

Got Marada at around 1170.

53 Hashi frags right now.

So roughly 1 frag every like 30-35 scrolls. Depends on the RNG. Generally you'll be in the high 20's or low 30's when you get an SR.