about Total Person Time vs Total Reviewer Time
I'm answering a question I found on a previous closed thread Collaborator forum: Total Person Time vs. Total Reviewer Time because I was looking for the answer too.
Total Reviewer Time is a subset of the Total Person Time. I think it counts the total time spent by reviewers who actually approved the document. You can test this by summing the Person-Hours for each person with State=Approved and compare to the Total Reviewer Time.