When someone is getting used to RATs they may put the legend at the top for easier reference. However, once they no longer need it they may want to move it to the bottom so that the node list isn't pushed down. When you do this it puts the legend above the "I've check all of these" button, but it would seem better if the legend was below "I've check all of these" so it's less likely need to scroll down and probably less distance to move the mouse to get to it.