The visualisation shows the top 1000 known exoplanets (as of 2016) by radius. The data for this visualisation comes from ‘Cosmos: The Infographic Book of Space’.
The sizes of circles range from 14x to 28x the radius of Earth. The reason being is that the 100th largest known exoplanet is 14x times the radius of Earth. The largest exoplanet is 28x the size. The colour of the cicles are also based on the radius, yellow is largest.