Are the 4 featured SSR jewel rolls given 15% chances each or is it 15% chance then another 25% chance for each?

I didn't noticed the changes due to jewel saving. Does it worth the risk for Osiris or should I keep saving for Thanatos for my main?

Also, should I start babysitting this barely used Amaterasu-Osiris account after Ifrit and SSR Amon dropped few minutes ago? I was aiming for Mars on this account but they dropped instead after 40 rolls. It's hard to decide since it's quite an even split between Dark and Fire.