To create an iCal compatible with Check-in Scan on Booking.com, you need to make a configuration change to only display accepted bookings.
Within the "Calendar & Pricing" section, click on "Sync calendar".
Click on the bottom-right button that says "Change".
Select "Booked dates only" and click "Save".
Next, click on "Add calendar connection" and then on "Skip this step".
In the window that appears, enter "Check-in Scan" in the "Name your calendar connection" field and click "Export calendar".
Finally, copy the link by clicking "Copy link" and then click "Done".
Now go to the Check-in Scan user panel, navigate to the property's "ICAL" tab, enter the calendar link, and click "Import iCal".
In a few minutes, the synchronized bookings would start appearing in the "Reservations" tab.