If you don't want the pressure on your pen to affect the brush size, set this parameter to 100%.
The minimum size is set to a percentage of your brush tip's maximum size, which is 25% by default. If you are using a pressure-sensitive pen tablet, use the Minimum Size slider to set the size of your brush when using your pen with very little pressure.When drawing with a pressure-sensitive pen tablet, your brush's size will range between its minimum and maximum size, depending on the amount of pressure you put on the pen when drawing. NOTE: When drawing with a mouse, your brush is always at its maximum size.
