Here is how to create a Booking Engine Profile.
You will see here your default profile and also there is a link for each room type so people can book 1 room type only.
Why Multiple Profiles?
Sometimes you want to have a booking engine for a specific agent, company, wedding party etc. You can give them their own link to their own special IBE. You can choose the rates and rooms they have access to and you have some other settings to control like if they need to have a credit card or not.