I'm a self-taught composer currently trying to make my way through Arnold Schoenberg's "Theory of Harmony." I'm unfamiliar with what the numbers super-scripting certain notes means- is it the octave?
Schoenberg is (as mentioned above) writing down the harmonics of a tone. "Klang" is German for "tone" in English (but I will resist the obvious jokes).
The harmonics of an ideal string (as opposed to a real string which has weight and tension) have the ratios, 1,2,3,4,5.... times the fundamental. For a fundamental of "c" the next note would have a ratio, of 2/1 (c1)[I don't know how to make sub and superscript on this board] the string vibrates a half-length. Then next is g1 (vibrating at 3x the fundmental) then c2 (4) then e2 (5) then g3 (6) and now b3 (at 7:1, this is really out of tune according the the "just scale."
It seems that Schoenberg isn't exactly correct in his list. (As noted above).