For example, you set the ISO to 800, the shutter speed to 1/50 at 25fps, you are hoping to shoot at F2.8 but the light meter tells you should set your aperture to F6.3. So here you have too much light hitting the subject, to rectify simply adjust the lighting or lower the ISO and try again, and hopefully your light meter will edge closer to F2.8. Make sure you are placing the light meter where you are wanting the focus of the shot to be, there’s no point taking a light reading from behind the camera!