How does the Sposobin T.S.D harmonic notation work?

Three chords built on the dominant (I scale) are the main chords, major is labeled T, minor is labeled t.

Three chords built on the subordinate (IV scale) are the main subordinate chords, major is labeled S, natural minor and harmonic minor are labeled s. Melodic minor is labeled S if the VI scale is raised. harmonic major is labeled s. Melodic major is labeled s after the VI scale is lowered.

Three chords built on the dominant (V scale) are the subordinate chords, major is labeled D, natural minor is labeled d, harmonic minor is labeled D.

Three chords built on the dominant （The triads built on the dominant (V) are the dominant chords, major is labeled D, natural minor is labeled d, harmonic minor is labeled D, and melodic minor is labeled D if the seventh step is raised.

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