The first drawing below illustrates the octave relationships on a 24-key mbira. A 22-key mbira would not have the outermost key on each side. The second drawing shows the octave relationships on a 28-key mavembe (gandanga) tuning mbira.
In these drawings, all octaves of the same note are the same color. Memorizing these octave relationships makes it much easier to learn to play mbira.