Units of real space wavefunction (51)

dmpz

Dear Users,

What are the units for the real space wave function obtained from commands 511 and 512? I am trying to understand why the isosurface values ​​are so small. In molecular DFT values ​​around 0.02 - 0.05 might be expected to display the molecular orbital isosurface, but after reproducing the CO example given in the 2021 Computer Physics Communications paper I see that isosurface values ​​around 1e-8 for CHGCAR format and 1e-7 for .cube format give a nice picture. Further, why would the different file formats lead to different isosurface values providing the same image?
I have attached an image showing the HOMO obtained from Turbomole with an isosurface value of 0.05 and one from VASP using 551 with an isovalue of 3e-8. Please help me to understand the units used in VASP and the transformation performed by VASPKIT.

Thank you for your time.

Best,
dmpz