Well, I'm remiss in asking, perhaps, before I get in some more time with my own "Rack" here, but it just seems a sensible question... in the non-virtual world! I'm going back in...but, see if this makes sense (heh):
When I go to Effects in CEP, I get into a window (Properties...?) which lets me choose parameters of the chosen effect; including volume, dry/wet, that kind of thing. I haven't spent enough time with this Rack yet, but I'd guess those faders would be relative volumes between the "chained" effects (i.e, Rack) going into a particular channel's insert.
Whatever you set an individual effect at (in Properties window) volume/gain-wise, becomes "0db" on you Rack fader, since we're now talking about how much of the effect you tweaked in Properties getting to go into the track. I'm just thinking this makes sense...
So, in Properties you get the actual 'mix' of your individual effect, and in the Rack you adjust the amount of it (%) you want for your track. I'll bet that last fader represents the Aux send or 'FX' knob on a channel strip, adding the total of the individual chained effects (Rack) to your channel. Pretty analog, unless I'm totally wrong. Yack...
Rog.
P.S. The Mackie board I mentioned has 4 Aux sends in a channel strip. In case anyone cares.