It should be 40-70, but you get lucky sometimes. Also, I believe you're required to spend seals in the treasure if you want a rare. I spent zero seals in Seal Treasure, and I've never gotten a designated rare from it. As for Tendo, I spent 20, and I've gotten rares as free pulls.
dont quote me on this i think u gonna get designated ninja every 30-50 on tendo, i mean somehow i have 3 pain's already without spending any seals on tendo treasure