I added a feature(through your support)where clients would

Hello,
I added a feature(through your support)where clients would be allowed to book themselves in a little later than my available hours....eg: I close at 8pm and people have the ability to book a 60min session at 7:45pm.
I would like to remove this feature and only allow them to book within my available hours.
Please let me know how I can get it back a situation where clients cannot book outside of my scheduled hour.
Thanks
Droughan