When we’re talking about a typical major or minor scale, the octave falls by the 8th note of the scale.
E.g., a C-major scale consists of:
C D E F G A B C(one octave above your starting C)
1 2 3 4 5 6 7 8
Now, if we’re doing a whole tone scale, there’s only 7. If a half tone scale, 13.