24mm vs. 27mm wheel offset??

I have been reading about wheel offsets, and they talk about postive and negative offset...blah blah blah.....

I have an 01 GT axle in my notch, and 17X8 wheels come dead even with the quarter panel. 17X9 FR500's have a +24 mm offset. 17X10.5 FR500's have a +27mm offest. Can somebody explain to me this...

Is the it the bigger the number the more the wheel will stick out or the more it will sit inward. One of the links I got from stangnet said that the bigger the number the more it will sit inward. Is this true?

That is a better website than most I have seen. I am still having trouble picturing it, but I guess that is my answer. So with the 01 axle longer by 1-1/2 inches on each side I should go with the 17X10.5" FR500's since the 27mm will sit in more and more wheel will be under the car.