Color bar with discrete colors

I am confused about what is happening when I add a color bar to an image using discrete colors. I took the example code for and added a color bar to it.

The color bar show 9, not 10, equal sized pieces. I figured that the 10th color could be just a strip on top which was never used in the plot. Therefor I set the limits of the plot to -0.1 and 0.1 to ensure that parts of the image were below the minimum and parts were above the maximum. Now I can clearly see 10 colors on the plot, but only 9 on the color bar. Was this the intention? Is there another method of putting a color bar on a contour plot of this type?

This is how I modified

After the call to imshow in line 34, I added
clim(vmin = -0.1, vmax = 0.1)


Ms. Carol A. Leger
SRI International Phone: (650) 859-4114
333 Ravenswood Avenue G-273
Menlo Park, CA 94025 e-mail: leger@...392...