Why does my QuickScan report show an issue from a previous scan that I did not include in the parameters?

QuickScan merges the results from the scan of your parameters with the results from previous scans. Old issues may be present but the scan has only considered the parameters that were used. 

When you do a SmartScan, the resulting report is a hybrid. It shows the new data for the pages that were scanned, combined with the existing data from the last full scan that included all other pages.