Are the values provided for this term mean the error value (how close the calculated automatic values are to the actual GCP points that were manually collected? or does it imply the accuracy of the manual points in terms of how they scaled to the map?
The mean error value refers to the mean/average error in each direction (X,Y,Z).
How are the GCP Errors defined in the Quality Report?
The error is each direction corresponds to the difference between the computed GCP 3D point and the original position in X direction (original position (Manually collected) - computed position (Calculated automatic values)).
Quality report specifications
Hope this helps,