There are 6 strings 22, 6 strings 42, 6 strings 50 and 6 strings 57, including the fault-tolerant 2 field. Take 6-string 22 as an example: this string includes 15, 4-string 1, 6 notes 5-string 1, 1 notes 6-string 1. You are wrong in two fields and five strings 1. The bonus is calculated by multiplying the correct four sp values, and then multiplying by 2, which is the double bonus. If it's multiple purchases, multiply it multiple times to get the final bonus.