You can find statistics about an instructor by going to a skill's page and clicking the instructor's profile picture. This takes you to the instructor's profile. At the top of the page you'll find the statistics of the instructor:
This is the average rating of all the instructor's bookings.
This is the total number of hours the instructor has been booked for.
This is the total number of unique customers the instructor has had.
Don't confuse these statistics with the ones shown on a skill's page. The statistics shown on a skill's page are for that skill in particular.
If you want to learn more about a skill's statistics, then please read this article.