Duration in Map Summary Email vs. UI
The duration value in the email is greater than what you see in the UI. This is true for maps and scans in VM, PA/PC, and PCI.
When a scan/map is finished, you can see the duration displayed throughout the UI (in the preview pane, scan results and reports, activity log, etc). The duration displayed in the UI is the scan run time, which represents the time the scan was actively running.
If you have notifications turned on, then you receive an email notification when the scan is finished and the results are processed. This email notification shows a different duration value for the scan. This duration is the scan run time and the time it took to upload and process the results.
In the images below, you can see that the map titled My Discovery Map ran for 3 minutes and 46 seconds, but the email notification shows a duration of 6 minutes and 1 second.
Preview Pane
The Maps list preview pane shows a duration of 00:03:46.

Scan/Map Results
The results report shows a duration of 00:03:46.

Activity Log
The Activity Log entry for the finished map shows a duration of 00:03:46.

Email Notification
The email notification displays a duration of 00:06:01. Again, this value represents the runtime plus the time required for results upload and processing, so it is greater than what appears in the UI.