The Edit Copy... appears because the data source that is being used is a published data source. The original calculation cannot be edited because it was published with the data source. So essentially it would be like trying to change a field. Therefore, the calculation can be edited, but it will create a new calculation so that the original is not altered. Hope this makes sense!
That makes perfect sense. I won't go into the details of how certain things became derailed in moving from a direct database connection, to creating an extract, publishing the extract, and then connecting to this published source, but I can certainly manage.