audio alchemy dti pro32 help

lost my owners manual and am not certain which configuration of lights gives 24 bit dither. i know when the bottom 2 lights are lit, i am getting 20 bit dither. please help
On, Off, On
I thought you held one button in;while pressing the other to cycle thru and watch the approiate led.
Sorry for being unclear; top led on, middle led off, bottom led on; cycle through until this configuration occurs, and 24 bit dither occurs. Ed