Yepper, 1/2 is half a measure, default is 1/16. You could think of it as showing how fine it will snap. You could quantize to say, 64th notes, but you probably wouldn't see much of a shift in notes. Not only that, I've noticed Reason won't quantize notes to the nearest hundredth (maybe just my settings?)

Usually basslines and comping I'll fix by hand since I want it 100% dead on, and leads / melodies I kind of just quantize once with 16th snap and let it float wherever, unless it's totally jacked up then I fix by hand