Notice that on the x-axis (pH), 7.4, normal pH is in the middle. Notice that it crosses the y-axis (bicarb), at 24. That location with coordinates of 7.4 on the x-axis and 24 on the y-axis is called normal. Notice that the graph is like three intersecting curves drawn with a paintbrush with broad strokes. Notice that they are not straight lines but curves. The metabolic disorder curve runs from bottom-left to top right. The chronic respiratory disorder curve runs from the top-left to the bottom-right. And the acute respiratory disorder curve runs from toward the middle from somewhat middle-left to somewhat bottom-right.
Acid-Base Nomogram. Image from Wikimedia Commons.
Sources/References
Source of image: https://upload.wikimedia.org/wikipedia/commons/1/18/Acid-base_nomogram.svg