Ok Gonk, I went the on line manual. Sounds pretty basic and cleared up some things for me. tell me if I am starting this correctly.

Set the master control volume on the 990 to 0.

Go to channel calibration. All levels set to 0db's

Turn on spl meter and set to slow and c weight.

Now from here I have some questions. I have a Galaxy CM140 SPL Digital meter. There is a level selection mode,
Lo=32 - 80dbs
Med=50 - 100db
Hi=80 - 130db
Which one do I use?

Second, the digital cm140 cannot be adjusted manually to a 0 setting. Do I ignore the zero setting and make adjustments using the channel calibration until the meter reads 75db's.
The meter has a range from 32db to 140db at frequencies between 31.5hz and 8kz.

Thanks