Hello - Recently I have been trying to create a custom metrics where it will populate a Business Hours a service/incident ticket is assigned to ticket group DevOps - so far I have had no luck with support from Zendesk or any of the online resources. 

THEN VALUE(Field changes time  (min))/60 

ENDIF

Using the above formula for calendar hours, I was only able to calculate a few tickets with a non value of zero and majority of the ticket had no value to this metrics formula. 

Any suggestion on how I should tackle this?