Referring to international practice, the joint credit rating divides the credit quality grades of bond funds into seven grades: AAAf, AAf, Af, BBBf, BBf, Bf and CCCf, among which AAf~CCCf can be adjusted by "+"or "-",and the highest grade is AAAf. The meaning of each level is as follows:

AAAf level: the fund portfolio has the strongest protection against the losses caused by the credit risk of fund assets.

AAf level: the fund portfolio has a strong protection against the losses caused by the credit risk of fund assets.

Af level: the fund portfolio has a strong ability to protect the losses caused by the credit risk of fund assets.

BBBf level: the protection of the fund portfolio to the losses caused by the credit risk of the fund assets is general.

BBf: There is uncertainty in protecting the fund portfolio from losses caused by the credit risk of fund assets.

Class Bf: The fund portfolio has poor protection against losses caused by the credit risk of fund assets.

CCCf level: the fund portfolio has the worst protection against the losses caused by the credit risk of fund assets.