A Little help with hand held exposure meter and my 20D

I am finding I need A Little help with a hand held exposure meter.
My current meter, which I have just purchased, is a Sekonic 308 B. I believe I understand the meter and how it works, but I am having difficulty regarding how I use it with my 20D
For example:
I am working in the ambient light mode; plug in the speed for which I want the shutter speed and the ISO I wish to work at
I meter with the meter.
After doing this I get a reading, lets say F/4.0 and a shutter speed at 1/25th at 100 ISO, so far so good.
Now the main reason I ask for help. In addition to these readings, I get another reading that indicates plus 1/3, 1/2, 2/3, etcetera.
The instructions direct me to "and here I'm confused" that this represents to increase the exposure by that many thirds, tenths etcetera? How, do you increase the exposure by those numbers with a 20D; still preserve the number for aperture and shutter speed? Or am I not doing this right?
I am assuming that you would'nt change anything in exposure compensation?

Not sure what the 308 does... maybe its the same as the 558 which I own. when you take a reading, there is a 3rd number which is in 1/10th reading of the current aperture. This is for light ratio, which the camera can't compensate, but you can add lights and reflectors to increase or decrease

So for example. If you have a half and half lighting on a specific subject. At ISO 100 f/8, you get a reading of 1/125 at 1/10, now you can take another reading of the side of it, and it might be 3/10. Take another reading from the opposite side it might say 6/10(3/5). what that tells you is that one side is brighter than the other by 3/10 of a stop in that particular aperture and shuttler speed. So in this case you might want to add a reflector to one side to get your 1/2 ratio. In the case of the meter it would be 5/10

I hope that is the number you are referring to.

Yes I see what you are saying and it does make sense. This ambient reading on my 308 is showing me what thw lightings measurement is and if I was to ad a second lighting source I would have to determine what would be my main vs: my ambinet lighting to determine the ratio. Ufortunately, I don't have the memory features built into my meter that the 558 does, so I would have to write them down and reset. Thanks much!
Russ