The resolve by KPI is setting as per a custom date-time field whose value will set by when the email is converted to case.
In SLA , the holiday list and business hours are configured as 9 am-5 pm. (8 hours)
The failure condition is set as per working hours for ex if 10 working days= 80 hours.
Now , the problem is whenever the SLA is triggered ,Resolve by time is populated outside business hours i.e. 10:22 PM.