How can I account for business hours when measuring first response time SLA?

How can I account for business hours when measuring first response time SLA?

I am just starting to use Zoho Reports for our ServiceDesk Plus.  It appears that first response time is measured over 24hr period.  For example, in the Average First Response Time report and Average First Response Time by Technician.

I'm hoping to get some help in figuring out how to account for the operational hours that we have defined in SDP?

Thank you for your help
-Mark