I'm reading an article about L. casei effect on microbiome in rats with induced-RA. I understand the concept of healthy plane but I can't understand what's the meaning of this graphic. According with the article, L. casei group showed a healthy plane pattern at day 7 and day 30, however I see the lines like a positive relation towards disease plane so that's confusing me a lot

This is the article: Article A single bacterium restores the microbiome dysbiosis to prot...