Characters per Minute: This unit of measure is recommended if you are trying to achieve very slow character based speeds.
Characters per Second: This unit of measure may be desired if you want longer words to display for longer periods of time than shorter words. Note: You may want Variable Delay option set (refer to Delay Options).
Words per Minute: This is the traditional unit of measure for Reading Speed. You may desire this unit of measure when displaying more than a few words per flash.