Each project has a maximum number of banding scenarios you are allowed to create based on your access type.  The minimum number of banding scenarios for any project is 5, if you surpass your maximum you are allowed you can alter or delete each scenario that has already been created.

You may decide to create multiple banding scenarios if you are in the process of determining you Pay Equity Plan so that you can compare the scenarios.  Also you may have different pay bands for your compensation structure and your Pay Equity Plan and would like to maintain both in the Compensation Tool.