Just curious

So I was looking at my cycle history all the way back to when I first started using the app, and when I looked at my cycle lengths under cycle history I noticed all these green little arrows going across my cycle for that month does anyone know what those are for or know what they mean? I have been meaning to ask and just hadn't yet. If anyone knows could someone please tell me!

Also it is my 16th day on my cycle after miscarrying is that normal or should I possibly see a doctor. The line on my pregnancy test is much lighter and almost gone now so hcg is going away. Is it normal to have a cycle this long after miscarriage? I know everyone is different. My last miscarriage wasn't like this at all though. Thank you for the help!