The Visibility section represents two parameters for your and each competitor's site:
ETV (Estimated Traffic Value) shows the amount of traffic that your site and your competitors’ ones gain for all key queries that have been added to the project. The calculation is based on the Search Volume of each request and traffic distribution coefficient in the SERP.
SVV (Search Visibility Value) shows the overall visibility of the domain for key queries which are added to the project, measured as a percentage. 100% SVV means that all keywords that are in the project are in TOP1.
Distribution coefficient is defined by the following table: