Since you created it, what do the green circles represent? I guess some kind of big tree but I couldn't quite figure it out. On the other hand, I was consciously thinking whilst running that this is one of the few areas I know where the root stocks obvious in the forest tend to correlate to the ones on the map!
Got it in one - the trees I felt stood out as forest giants, with the size threshold for qualifying as a giant highly context dependent, i.e. whatever struck me as I was fieldchecking with the thought, "Wow, that's a huge tree!". In our area, that generally means a significantly larger than average deciduous tree, with a unitary trunk (not split into two or three trunks), surrounded by other similar trees varying from much to only slightly smaller. I can understand why not everyone likes to have them mapped, though Dave Linthicum is a fan (told me so after running at Rosaryville, my first forest map, for the first time). They gave me fits too - I ended up carrying a tape measure around with me while field checking so I could measure the circumference of trunks at my sternum height and set a fairly objective, more or less consistent threshold across the map.