not uncommon for hand times to be a tenth of a second faster than a laser timed 40. This is why it looks like a lot of players that run at the NFL combine "get faster" between then and their pro day a few weeks after. But its usually more to do with the method of recording the time than the player improving their speed. Not to say that doesn't happen or that this is the case 100% of the time, just that it happens quite often