Bring a watch with a second hand (or digital with a readout) so you can see if 1 second is on or not. The shorter speeds are evaluated by just seeing and hearing (to the best of your ability) if they seem 1/2 the duration of the next longer speed. 1/500, if it's close to accurate, is almost impossible to see when looking at the shutter through the front of the lens. Many cameras' shutter are really slow once you get down lower than 1/15; the question is whether you'll ever even use those speeds. However, if they're off, it's an indication the whole shutter will need cleaning at some point.