The 'ratio' is between the specialization's representation in the meta vs. To rank all specializations, uses something called Meta Ratio Score.
The site plots all runs available from the Blizzard API (excluding the Chinese region) on a single ridge plot, so the data will be different from our Shadowlands Mythic+ Rankings maintained by Petko. In this post, we look at the tier list for Mythic+ based on the data gathered by. We're looking at the first class tier list for Mythic+ in Patch 9.1.5.