'Modify Exposure with +/- Keys'

That message only appears if you click on the heading text of an option. If you don't want to see it, you can simply click on any another area except the heading text.

For example, if you want to edit Exposure without seeing the message, click its slider, the slider bar, or the numeric value…but not the word Exposure. If you make a habit of not clicking on heading text, you'll never see that message again.

The message isn't actually there for "real time" editing since you can do that with the mouse and the sliders. The message is actually for keyboard-driven editing. When you click an option's heading text and that message comes up, you can now use the < and > keys to change the value.

Where this really becomes useful is when you want edit the image with all panels hidden so that you can see the entire image as large as possible. You press < and > to change the selection option (the message tells you which option is selected when panels are hidden), and then you press - and + to change the value.