Help! Trouble setting levels on 442 Interface!

[CafeCinema]

I'm having challenges calibrating my 442's inputs and outputs in relation to my Mackie mixer, for ProTools.
I'm using the Calibration Tool, and the directions from Digidesign.
The directions say that the Headroom is best set between (-15db to -20db)...
...I have a Mackie mixer that claims -28db!...according to the Digi manual(in their example of "if you have a -15db mixer then set the Headroom level to (-15db),etc.")
...So I set the level to -28db...IS THIS TOO LOW? I just did what it said.

Next, It recommends either a tone generator or a mixer that has a 0 VU tone.
I have neither so I got creative.
I recorded the Calibration Tools Tone directly into my DAT at 0db(on both channels)
I then ran this signal (setting levels the Mackie way...with the SOLO and SPL)to set my mixer at 0 VU. Then I followed the directions...
...I've tried various things and scenarios....
CAN ANYONE GIVE ME THE "CALIBRATING YOUR 442 FOR DUMMIES?"
Please, I find that Digidesign manuals can sometimes beat around the bush and their examples usually just repeat themselves. Whoever wrote these must be fired!
The 4.0 version manual seems better, but I'm stuck in NuBus land...
Signed,
Singleton 'THANKS IN ADVANCE!!!!!!'
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