Why Rollup Calculator is not applied properly in Vulnerability Group. All group risk rating is None5

[Akshat01082000]

In Remediation task (Vulnerability Group) all  record risk rating in 5-None and risk score is 0.why?? 

1) here we are running our own remediation task rule. Not OOTB.

2) And we haven't change the OOTB Rollup calculator.

so why it is not working property.