Before October of 2015, only four studios were shown. In October of 2015 the Scratch Website was redesigned and the number of featured studios at a time was changed to five.
The Featured Studios section is the second row from the top.
In the 1.x website, before the release of 2.0, there was an analogous list in the sidebar, called "Featured Galleries". It only showed 3 galleries at a time.