Joining communities on app

So I was browsing on the app and happened to see one of my communities post that another community was their neighbor now. I went to that page and poked around a bit to try to join and managed to do so by pressing the green plus sign on the bottom right of the screen. Not sure if that is a feature or not. Anyway, now that community shows up on my community list on my app but not on my desktop version. I have a few screenshots but when I made this an image post it only wanted to accept one image and I wasn't sure which picture would work best so shrug.

Also for some reason when I open up the tags (edit:specifically the tags on this post. I'm not sure about anywhere else) it says 0/2, and when I click one it then says 5/6, then when I click another it says 6/6.