Most report options, for example: reporting period, mailbox selection or filters, are saved each time you run a report so that you can re-use them in the next report. This is meant to simplify the input of frequently used options.
Should you need to reset those options to default values, simply locate and rename or delete the LastValuesxxx.ini file.
The default location of the LastValuesxxx.ini file is the user's Documents\Promodag folder, see: Default paths for installation and settings.