What does the number of Y axis mean?

Depmap PFDN2

I want to know the expression differences of the gene or protein between two liver cell lines.
In this picture, the X axis seems to mean transcripts per million of expression of the gene PFDN2, I think.
It is showed “Relative protein expression proteomics” on Y axis, but what is the measure of this?
The point of Huh7 shows X; meaning log2(TPM+1)=7.473 and Y=-0.1722, then what does the number of Y axis mean?

Would you like to tell how to read this graph?

(I’m not sure if you attempted to attach a screen shot, but I don’t see one on your post, so I’m guessing a bit what the plot looked like)

It sounds like you’re asking how is “Relative protein expression proteomics” defined, correct?

I believe this is probably the units shown for the proteomics data from this paper: Quantitative Proteomics of the Cancer Cell Line Encyclopedia.

If I recall correctly, the method used to do the protein quanitification cannot report absolute quantities but instead quantified the proteins relative to a reference.

Looking at their website just now, I notice that they appear to have written a guide for to aid biologists to interpret their data titled, “A Guide to the Quantitative Proteomic Profiles of the Cancer Cell Line Encyclopedia” This document will likely have the answers to any questions you have about this data.