Available count not decreased after a reservation

I have a hour based reservation system. Everyday there are 10 slots which can be reserved. At first every date shows 10 Uygun (10 Available) correctly, however when someone reserved an hour, it continues to show 10 reserved even though there are 9 available left.

You can check it from this page:
https://www.davinciescape.com/index.php/oyunlar/kayip-hazine/

23 Temmuz (July) has a reservation but it still shows 10 Uygun (Available). You can make fake reservations to test if you want, provided that you state that is a fake reservation in message part.

https://www.ads-software.com/plugins/booking-system/