The chart is as non-specific as could be. It improved in some very vague metric by some amount at different (increasing) levels of training.

Isn't the y axis just what portion of the open problems it could solve? The axis is unlabelled though, I'll give you that

The x-axis label of the chart is test-time compute. Doesn't this relate to inference ("thinking level") instead of training?

That's fair, but at least the chart has an axis. :) Since openai just released astra, I was more surprised that they would publicly show any gap to their (presumably SOTA) internal model.