The green line is the projected future trajectory of the Dragon spacecraft relative to the ISS, assuming no outside forces (eg. thruster firings). Once Dragon is docked to the ISS, it's meaningless, as there's a rather large outside force in the form of the docking latches.

As mentioned on the livestream, the green line is the projected future trajectory of the Dragon spacecraft relative to the ISS, assuming no outside forces (eg. thruster firings). Once Dragon is docked to the ISS, it's meaningless, as there's a rather large outside force in the form of the docking latches.