Sometimes its important to compare 2 scans to see if the vulnerabilities you fixed show up again...
To create a Delta Scan simply choose the reports -- in this example, simply click on the blue '20' below:
This pulls up the scan job and you can see the reports that have run.
Simply choose 2 of the reports, then choose the 'actions' button and choose 'Delta Report'.
You will see a preview of the report and you can filter down to exactly what you want to see in the report--then press 'Create Report'.
The report will show up in the MSP Portal and will look like the following: