Parameters (considering normal people is 1);
E rank; 10
E+ rank; 15
D- Rank; 25
D rank; 50
D+ rank; 75
C- Rank; 100
C rank; 150
C+ rank; 250
B- Rank; 350
B rank; 500
B+ rank; 750
B++ rank; 1000
A- Rank; 2500
A rank; 5000
A+ rank; 7500
A++ rank; 10000
A+++ rank; 15000
S- Rank; 20000
S rank; 25000
S+ rank; 35000
Skills classification;
E+ rank; 5% increase
D- Rank; 15% increase
D rank; 25% increase
D+ rank; 40% increase
C- Rank; 55% increase
C rank; 70% increase
C+ rank; 90% increase
B- Rank; 110% increase
B rank; 130% increase
B+ rank; 155% increase
A- Rank; 180% increase
A rank; 2 fold increase
A+ rank; 2.5 fold increase
S- to S+ rank; 3-5 fold increase
SS rank; 10 fold increase
Also from A- rank, damage can be easily controlled