Go to "Reviews & Survey" section. Make sure the status of review is "Active". Find in the list or by using a searching bar the required review-period and click on it.
You will find yourself on a period's page. Here in the header you'll see the current progress of a review:
How many members completed self-review
How many reviewers completed reviews of their peers
You also can scroll down to see Reviewers' Progress right in the table.
