If you want to do some of your own analysis in a spreadsheet, then you can download a table of call information. Go to "Reporting > Calls" in the main navigation menu.
Select the pre-built ranges or set a custom date-time range:
Select the set of calls you want to get data for.
At the top, you find a field that tells you how many results you got. You can download those results as CSV by clicking on the blue button. Click on it and wait. Depending on the number of results this might take a few minutes.
you can download a maximum of 5000 records. So if your results show you more than 5000, you can either narrow the time span or filter the calls you want to investigate (e.g. all calls shorter than 30 sec. and not connected to an agent).