Rebooking changes an existing commitment when the person, dates or hours need to change. Edit the booking you intend to replace. Adding a second booking without removing the first can double the demand on a person and inflate the forecast.
Read the booking ID as well as the person and role. A person can have several assignments to the same project, and the provisional reservation may be a different record from a confirmed commitment. When you move a booking, keep its weekly hours and date range unless the request changes them. The receiving person must satisfy the role and have enough capacity in every included week. Removing a reservation should remove only that tentative record; it shouldn't remove the role itself or unrelated confirmed work. Reconcile the schedule after the change, especially around the old and new endpoint weeks.