Change your rules for the online booking at dinnerbooking.com.
Go to Online Booking -> Global Settings
Set the rules
Pax allowed per booking controls the minimum and maximum number of guests per booking.
Cut time closes for new bookings during service. If service starts at 12.00, cut time Lunch can be set to 11.30.
At 11.30 all lunch times that day will then be closed, only allowing guest to book for dinner
No online bookings later than specified hours prior to arrival, set a limit for when a booking can be made.
If set to 1 hour, and a guest want a booking for 18.00, he has to create it at 17.00 the latest.
Max hours allowed in advance for booking controls how many days in the future the guest can book.
If set to 30, guests can only make a booking for the next 30 days.