Edit Brush Dialog Box - Scaling Tab
These options let you progressively increase or decrease the size of objects in the brush. Use Line width to set the basic size of the objects.
Scaling changes by:
Random
Gives a random scaling change between objects. The slider limits the difference; for example, 50-200% limits the scaling to between 50% to 200% of the original size.
Pressure
This has an effect only when using a pressure-sensitive input device such as a graphics tablet. The scaling is controlled by the pressure you applied when creating the line.
Randomize
Generate a new random set of scaling changes. If you prefer the previous values, click Undo.