Soul Spring Eternal bug, CoC

I am not sure whats going on but I have Cast on Crit at quality 20%. at 100 spirit cost, a 10% reservation efficiency would bring me down to 90 cost, but for some reason it is at 91 spirit cost.

Additionally when I take Soul Springs Eternal, which has a 50% meta gem reservation efficiency, my spirit cost is 63???

10%+50% = 60% efficiency, Should it not be 40 spirit cost?

yeah im pretty sure im not calculating wrong

anyone have any input on this? hopefully GGG looks at this the math is not coming out right

10% increased Reservation Efficiency
The calculation method is as follows: 100÷（1+10%）≈90.9
so it is 91
Similarly, consider the case of a 60% increase Reservation Efficiency.
100÷（1+60%）=62.5
so it is 63

thanks for the explanation. the wording is not very intuitive

today i tried to use pure "cast on critical" skill without quality! and spirit reservation still 63 im sure it's a bug!