To move either thumb on a slider, left-click and drag it.
NOTE: If you leave the slider while sliding, the thumb
you were sliding will stay active until you release the mouse button or
enter another slider (thus activating that one).
You can notice this by its gray color.
If you notice a thumb is still gray for some reason even though you
have released the mouse button, you can click on that gray box to lock it
in position.
The radio buttons to the left of each slider are to enable you to use
keyboard shortcuts to move the thumbs for that slider.
Click on the radio button next to the slider that you would like the
keyboard shortcuts to act upon.
To move the left thumb you can use 1,2.
To move the right thumb you can use 8,9 or -,=.
