In some cases, you may wish to manually mark a reviewer's participation in your ARC as completed. To do so, please head to your ARC listings and find the ARC you'd like to mark them as having completed. Then, click the "# copies claimed" link.
You'll be greeted with a list of all participants for the ARC along with their email address. Locate the reviewer by either searching for their email address or finding them in the list.
Once you've identified the reviewer that you'd like to mark their pariticipation as completed, click the "Mark Review as Complete" link next to their name.
Once done, you should see their participation marked as complete (which can be undone if you wish).