Timing Marks

Okay so I was looking at my timing because I am running a bit rough and I was wondering what each of the marks are. I can see one in between with no mark I assume is 0 then above and below there is a 10 I assume above 10 atdc and below 10 btdc Then on the upper side there is another mark with no indication what is that? What mark should I be trying to get to? Right now I am slightly above the upper mark indicating 10 degrees.