As it is a flash meter, the shutter speed is irrelevant as the flash duration is very short compared with the time the shutter is open. What it will measure is the burst of light from your flash and give a reading of EV in relation to the set aperture. As your camera uses a leaf shutter, you should be able to use any speed up to the shortest. Just make sure you set the M-X lever to X when using electronic flash to get the correct synchronisation.