Details:

There are multiple Average Performance Rating by Groups columns within the system, and they are defined through the System Display Values.

 

Here are the default Out-of-the-box values: 

 

The labels corresponds to the Ad Hoc Reports column headers, as displayed below:

 

If the labels are updated, the labels are reflected only in the Aggregate Group under the Performance Plan Configurations, the column header within the Ad Hoc Reports will continue to use the Out-of-the-box values of "Peers, Subordinates, Managers, Others".