Does the first reply time reply take into account business hours?
The first reply time in Zendesk is calculated in calendar hours and business hours. Both results are stored with the ticket data.
To report on first reply time within business hours in Explore, search for metrics that contain Business hours in their title, for example, First reply time - Business hours (min).
For more information about reporting on first reply time, see the article: Explore recipe: Reporting on first reply time.