[![enter image description here](https://i.stack.imgur.com/U38eY.png)](https://i.stack.imgur.com/U38eY.png)

I find this graph incredibly confusing. Is it saying that when there is a decreased affinity (of hemoglobin to oxygen, I think?), the partial pressure of oxygen increases with the same percent saturation of hemoglobin? What does that even mean if that's the case?