The 'Results' column by default report ALL conversions. If they had installed a Lead event somewhere in their website, people who saw the ad and then visited that page would trigger a Pixel fire that would be attributed back to this ad and reported accordingly, but rolling over the conversions results would show the breakdown. I.e. which Custom Conversion/Event was fired due to this ad.
To filter the results to see what they care about, all they need to do is to Customise Columns and search/select Complete Registration. Please see screenshot.