Hi Martin,
Thanks so much for reaching out!
I’m sorry to hear that you are experiencing this issue with your tickets.
Sometimes tickets do not get removed from the total sales numbers for one reason or another. You can change this manually by going to the WooCommerce Product Page for the ticket in question. From there, you can manually change the total_sales custom field to reflect the actual number of tickets sold. This will update on your Attendees page as well.
I hope this helps, let me know how it goes!
Thanks,
Jaime