Modifying the available report templates (for example to only show the top 10 instead of top 100) is possible, but requires manual modifications. Please see How do I modify PRTG's report templates? for more details.
Disclaimer: The information in the Paessler Knowledge Base comes without warranty of any kind. Use at your own risk. Before applying any instructions please exercise proper system administrator housekeeping. You must make sure that a proper backup of all your data is available.