The arrow (that is in the red box) shows you what track is currently playing.
Here you can see what the next tracks are. You can click on the 3 vertical
dots after each track to remove that track if you no longer want it in the
playlist amongst a few other options.
If you ever have any issues with
BubbleDS Next
the best thing to do is to
completely shut it down and then reopen the app. Doing this will also force
the app to rescan the library and will help pick up a CD that you have just
imported. Tap on the Menu button in the top left corner at any point and
you will see this:
Now tap on
Exit
shown in the red box above and then re-open the app.