If you set the Log conflicts drop-down to Yes, this will alert and log a conflicting iCal booking that is trying to import for dates already blocked off in SuperControl.

The alert is visible on the payments reminder page (Bookings > Payment Reminders) - usually the first page seen after logging in: 

There is a link (review bookings) which will take you to a report to review the bookings that could not be imported:

We display:

• The date and time we attempted to import the booking from the iCal feed    
• The property    
• The start and end date of the attempted imported booking    
• The summary text from the iCal feed    
• The source of the iCal feed    
• The existing bookings in SuperControl which prevented the booking from being imported    
• A toggle to select some/all logs
• Button to retry - this will take you to the iCal importer script
• Button to delete - this will delete a single log entry
• Select all button - select all logs    
• Button to delete selected (logs) - if a log is checked then we will remove it