So notice that this partial pressure corresponds to the partial pressure inside our lungs. And this partial pressure of 40 mercury corresponds to the partial pressure inside the tissue of our body. Now, the blue curve is the curve that describes our relationship when we don't have any two three BPG present inside our blood plasma. But when we have two three BPG present, the red curve is the curve that describes the relationship between our hemoglobin and the partial pressure of oxygen. And notice that the red curve is shifted to the right of our blue curve. And that's exactly what we mean by shifting the curve to the right side.