Hi @aguseranalytics -- total session length only applies to mobile apps. The value you're seeing is in seconds, and it is calculated based on when the app is launched and when it is closed (it does not run in the background). There is a delay in sending the data as the data for that session is sent when the app is relaunched for the subsequent session.
Were you looking specifically for mobile apps or were you trying to find an equivalent for your website or other platforms?