Y-axis is a coefficient calculated using paragon, clear time and GR level.
Sorry for your confusion. This is from a performance analysis I carried out (many in the past). With the intend to come up with some figurative buff numbers so devs would not buff classes blindly. Which proved to be a nice way of measure as S12 balance patch showed.
Afterwards, as they kept buffing, balance was disturbed again.
I dont post the same stuff all the time so in case you are not familiar, the link to this analysis is below. You can follow them to reddit and find all my old posts on this topic. It has some numeric comparison merit. Which is only average and not exact.