How to calculate time in hours between two fields (date type) and display it in workload pie gadget?

[Stanislav Platonov]

The main goal is getting sum of all the time that teams spend for the first respond:

We have two date type fields in our project "Created" and "Date of First Response".

Also we use JIRA Charting Plugin to get a "Date of First Response".

We need to calculate time in hours between this two fields "Duration time of First Response" since date "Created" till "Date of First Response".

For instance:

"Created": 12-05-2021 18:19

"Date of First Response": 12-05-2021 22:36

"Duration time of First Response": 12-05-2021 4h17m

1) How to calculate "Duration time of First Response" and get time in hours between two fields (date type)?

2) How to display the result of calculation in workload pie gadget by teams?