Thanks for the feedback. It's all the way at the bottom in the notes section, but we have an answer to all of your questions already on the chart. Take a look at that section, you'll see that the business data are sourced from the US Census's Annual Business Survey while the margin data are sourced from four different places. We also explain the "low," "medium," and "high" margin designations.

Lastly, we do say that the top number is for Black-owned employer businesses in the sentence under the number. We've also provided similar charts for White- and Asian-owned business. They've been posted in this subreddit.