By default, the Forms in Coupon Reach's Opening time is 8 AM and the Closing time is 5 PM.
To change these, you can go to your Forms, then edit the form of your choice.
Then go to Step 2 (Properties) and click the Reservation Time field element to open it up and edit it. (In the Default form, it says "Around what time?")
Then you'll see a section on the right where you can change the opening time and close time that the form would show.