Description
The output data's geographic coordinate system (datum) is different than the data frame's. The coordinate system of an output is determined by the coordinate system of the input, or by the output coordinate system environment if set. If the coordinate system of an output is different than the data frame's, the layer is automatically transformed to the data frame's coordinate system. However, the underlying coordinate system of the data is unchanged.
Solution
This is a warning; no change is necessary. If the warning is unexpected, check the current setting of the output coordinate system environment. The default setting is set to Same as Input.