Question about the EQ section of the 488

[bardo]

Ok,bear with me now
The spec's read
High shelving 10Khz +/-12db
Mid 250hz to 5Khz +/-12db
Low shelving 100hz +/- 12db
Frequency response 20hz to 22khz
Now my question is,is the frequecy response my whole possible bandwidth?
For example:the high shelving Starts at 10khz to 22khz?and the low shelving Starts at 20hz to 100hz?
I get the mid.I have two controls for that.I it seems from the mid is I can set which freq I want to boost or cut from 250hz to 5Khz.
What I don't quite grasp is the single high and single low.
If I crank up(or down) the high+/- 12db,what frequency am I boosting(or cutting)?
Same with the lows.
Does anyone know the Q's listed for this EQ?
It was not listed in the spec's
Hope I was clear enough .
Thanks for the help.