Hi I cracked my Chord Studies for Electric Bass by Rich Appleman and Joseph Viola, © 1981, and have a question about what I'm reading. C major chord structures open the study, and the first example is 1, 3, 5, Maj7, 9, #11, 13(6). Under the stave and suggested fingering are notations: C is annotated as — E — and, below that, — A — The following 3 (E) and 5 (G) are annotated below the stave as: — A — and — D — And so on. What is this being shown? Thank you!