[carey]

You have a fencepost error; the notes in Western music in equal temperament are C, C♯/D♭, D, D♯/E♭, E, F, F♯/G♭, G, G♯/A♭, A, A♯/B♭, B, then c an octave higher is the thirteenth.

[dberst]

Ah thank you for the correction, I'm just a hobbyist and have not practiced in a few years

[carey]

It’s accurate to say that there are twelve intervals, anyway, which is the point you were making.