No. 19 brush not appearing as it should?

[blog]

I just wanted to know that how come the number 19 brush doesn't always appear the way it is here and appears like the one above it?
http://i3.photobucket.com/albums/y67/blog3000/brush.jpg

[Datameister]

The first one has pressure sensitivity set to only affect either Flow or Pressure. The second has pressure sensitivity set to affect both.