well, since I use reason, perhaps I can shed some light on this.
If you have the Quantizise button on while you are recording from a keyboard via midi, then the notes will attach to the closest note. (i.e. If you have it set on 1/2 notes, then everytime you press a key, it will only fall on 1/2 notes. So even if you are playing as fast as 1/16th notes, they will be layed down as 1/2 notes.) And thats the same for the other note values. Personally I like to play my piece, and then quantizise them. To do that, you just highlight every note you want quantizised, right click and choose quantizise. Then whatever value in the drop down box is there, thats how the notes will be quantizised.
I hope this helped.