When using the External Bookingform you will notice the notification bell in the top right ringing, and the number going up.
Deleting archiving the request will clean up your database. This article will tell you how.
Deleting an External Booking request
Click on the ringing bel to open your request.
Simply hover over the title of the request and the bin-icon will appear.
Click on it, to delete your External Booking request. You'll get an extra notification to check if you surely want to delete it.
Note: deleting this request will remove this booking request from your system.
External Advancing requests
You might also find some External Advancing requests here. To archive them, check out this article.