Spectrum: what does relative amplitude means,units used

Hi, I would like to know whether the source code of the Spectrum function can be shared or if not I would like to know what does this part means



I know that in electrical engineering for instance there are spectrums that give in the x axis the frequency and in the y axis the amplitude or "energy" of the wave (light, sound) but here I would like to know if this amplitude is measured in PIPs or Lots or units of the account currency or what so that I can derive better algorithms.

Thanks beforehand!

As far as I understand the algorithm, it is proportional to the energy. But it has no defined unit. It is relative to the amplitudes of the other frequencies.