I checked out the manual to try and confirm but it doesn't seem to say. I think they represent degrees of bearing, as in the solution says it should be here (on the line) but your dot is off by 0.5 degrees. Either that or some form of error or standard deviation. Honestly, it doesn't really matter (don't at me
). It's just worth noting that when you zoom in you can see more of the "error" in the dots in the stack, which can be too sensitive and cause you to spend too much time refining the solution.