This setting allows you to change the message displayed on the last page of the booking widget.
You can access this setting by clicking on Configuration > then click on Site Contents
On the right hand-side, look for section Web Bookings Messages and click on that section to expand it.
Locate setting: Standard Booking Confirmation Message
Click on the Edit button for that setting
Enter the text that you wish to display…
and then click on SAVE
The maximum number of characters allowed for that field is: 500