Interview duration in API

I have established a link with SS API and received the data for my test case. One of the information I was looking for is the duration of the interview. However, that column is empty. Is there a parameter I need to add to the API call?

If you navigate to http://YOUR_SERVER/apidocs/index and try executing interview stats endpoint you will get interview duration field in response. There is a small guide on how to get to the api page