7*11 = 77
77/.15 = 513.333 (approx 513)
If we account for slight error, this can round down to 512. This is important and I'm pretty sure this is case. This makes it 15.04%.
512 * .28 = 143.36, we can round this down to 143.
Then:
Ruby/Sapphire/Aquamarine = 4
Emerald/Amethyst/Garnet/Peridot = 5
Pearl = 5
(4*4*3) + (5*3*4) + (5*7) = 48 + 60 + 35 = 143
pretty sure of this tbh.
unless you're also factoring in round 8

the total # of points might be slightly too high, can't really tell, but it doesn't matter for the purposes of this calculation anyways