Cover Users: What do these green things mean?

So I’ve been wondering about this since the Star Wars: The Old Republic beta, what the heck do these green things above the enemy NPCs mean?

They only appear when you use, what I call “Natural Cover” meaning, boxes, rocks, pipes and anything else that belongs to the game environment. These icons never pop up if you use your portable cover.

What do they do?

I would like to imagine it means, you have a clear steady shot, accuracy and critical hit chances have been improved by X amounts of percent. But I’d like to have confirmation on this. What do they mean?

Leave me a comment if you know!