A set of vibe notes in for tuning.
On the graph, the X axis are the notes – this vibe goes from C to F. The Y axis are the cents above and below the zero line which is at A=440 Hertz. The fundamental pitch is the blue line which is generally flat (to be expected as the instrument is marked A=439Hz). However the red line is the 2nd Harmonic, and as can be seen it goes from massively sharp in the lower octaves of the instrument, to massively flat in the higher notes.
To bring the notes into tune both of these lines should read zero.