Certain data is kept when you close the Conversion Tool and retained for the next time the Tool is launched.
This include start and FFOA time, output file format and the paths for both importing .xml file and target output directory.
If you want to clear these values:
Shift/Command G or Go to Folder using path ~/Library/Preferences
Locate and trash
delete C:\ProgramData\Dolby\Atmos Conversion Tool\AtmosConversionTool.ini.