If you want the Distressor to sound clean don't light up more than 3-4 of the gain reduction LED's and keep all distortion settings off. Also, use the lower ratios like 2:1, 3:1, or 4:1.
If you want distortion and some heavier crunch then light up the gain reduction LED's into the orange and red ones, use the distortion settings, and also use the higher ratios. Distortion on the Distressor is quite pleasing, a beautiful sound and what these are known for. They can do clean quite well, although they are not known for that.
The 10:1 ratio is an optical compressor, a seperate circuit from the rest of the box.
Also, you'd probably want to begin with all knobs set to 4 or 5 as a starting point and then work from there.
Hope some of this helps.