Once you click on a course and on the professor's name, it shows their average rating and classes taught. However, each time you switch between "Course", "Both", and "Professor", in the top-right corner, the original number of classes taught gets multiplied. Below is an example after switching multiple times between these options. The original number of classes taught was 13.

I am using Google Chrome on a Dell Inspiron running Windows 10. The url is coursetable.com/catalog