With the vast majority of forks, you will find that they are slightly wider than their nominal size, and when a wheel is dropped in, they will need to be drawn in slightly by the tightening of the QR in the case of a road bike, or by tightening the nuts on a track bike. Some of my forks are closer fits than others, but they are all 'off' slightly compared to the standard width of the hub. This is intentional, as too small would be a bit of a pain to install a wheel in, although I did have one like that several bikes ago.