You have to include "Rater_ID" in the calculation, otherwise it only looks at the visit number pane:
Click on SUM(ScoreValue) under measure values and click "Edit Table Calculation"
In the "calculate the difference along" dropbox select "advanced"
Select Rater_ID and move it to the right side
Click apply / ok
I've changed it in the attached workbook.
PatientVisits.twbx.zip 25.5 KB
Sorry for the late reply. This solution worked perfectly. Thanks a lot