When working with multiple objectives, this parameter selects the index of the objective you want to work with. When you
query or modify an attribute associated with multiple objectives (ObjN, ObjNVal, etc.), the `ObjNumber` parameter will
determine which objective is actually affected. The value of this parameter should be less than the value of the NumObj
attribute (which captures the number of objectives in the model).

Please refer to the discussion of Multiple Objectives for more information on the use of alternative objectives.