Since the selenium will continue to work while it just enters the water bath I believe Aggie is suggesting that you remove it from the selenium (pull it) a little bit before it reaches the full tone you are aiming for. This way it will end up at the tone you wish due to the slight toning still happening in the water bath. If you remove it from the toner when it reaches the point you want it will over-tone during the time it takes for you to remove it, place it in the water bath, and for the water bath to stop the toning.