MIRtoolbox: problems with x-axis scaleing when plotting values provided by mirgetdata

For calculating and plotting spectra from an WAV-audio file I'm using the Music Informationen Tool MIRtoolbox (https://www.jyu.fi/hum/laitokset/musiikki/en/research/coe/materials/mirtoolbox). I'm trying to compare two spectra by subtracting one from the other.

Therefore I'm using the command mirspectrum spectrum_1 = mirspectrum('file.wav', 'some parameters here'). That gives me a nice plot and in my workspace I get 1x1 value variable. In order to be able to plot and calculate the data itself I use the command mirgetdata to extract the values from the 1x1-objects. But then the information of the x-axis-scaleing is lost and I got a wrong calues on the frequency axis when plotting. By dividing through a value xstr, depending on window-length used in mirspectrum, scaling gets better but it is still wrong. I just can't find a way to get the right scaleing. There is always a lot of blank space on the far right of the x-Axis as well.

I attached the script, maybe it is easier to understand what I'm trying to do. I would be thankful if someone has experience with mirgetdata and could tell me how to plot the right values on the frequency axis.