If you are unclear about what the three squares mean when you adjust Pen Pressure, please refer to the following article.
The X-axis represents the original pressure sensed by the tablet, and the Y-axis represents the adjusted pressure.
The curve shows the change of degree of input pressure and the change of degree of output pressure.
If it is a straight line, as shown in the following image, it means that the pressure perceived by the tablet is the same as the output pressure, and this is the default value.
Explanation of each control point(blue, yellow, and red squares)
1. The blue one cannot move up and down; it can only move left and right. It indicates the initial pressure of first touching the tablet. The more it moves to the right, the higher the pressure required for the first drawing.
2. The yellow and red squares control the curvature of the curve. The yellow one controls the former section, the red one controls the latter section, and the relative position of the yellow and red squares determines the middle part of the two sections.
The steeper the curve, the more sensitive the change of pressure. The smoother the curve, the slower the change of pressure.
These two squares control three-segment curves.