Is the duration column (see attached) calculating correctly or what goes into it besides db time and .net time?

I create an adapter, don't set keep open, use it to fetch a collection. It should then auto-close when done.

There can be a difference between the connection usage period duration time and the total DB times and .NET times. This is caused by the overhead inside the used ADO.NET provider to open / close a connection or commit a transaction, and overhead inside the used data-access system due to code executed after a connection was opened and before it was closed.

ref: Duration Explained