I am not sure what you are asking. If, for a desired exposure level, shutter speed is increased, the two remaining components of exposure can be used to compensate. Either increase the light sensitivity(ISO) or increase the size of the opening in the lenses to allow more light to strike the sensor, or both. What dot are you referring to? When shooting in manual mode you have manual control of all 3 of the base elements of exposure and any changes made will reflect on the light meter display in at the bottom mid right portion of the viewfinder. In Aperture or Shutter priority modes plus any of the Auto or Scene modes the meter disappears but the shutter speed, ISO(if selected to display) and aperture are displayed. For example, if you are in Aperture priority mode and have set the aperture to f/4 and ISO is 400, the speed will be adjusted by the camera to expose well for the scene light level it is seeing. If the calculated shutter speed is too low for a handheld shot, you have a number of choices; use a tripod, increase ISO to have the camera recalculate a new, faster shutter speed or change the aperture to a smaller number(larger opening), say f/2.8.