For those of you that are trying to figure out your square footage of your zones, Google Maps (http://maps.google.com) will tell you exactly what you're sq. footage is and then you can use this in your zone settings. I did not see anyone mention it here, so I thought I would throw it out.
1) Open a web browser and goto http://maps.google.com
2) Enter the address of the lawn in question.
3) In the lower left corner of the map click on the "Earth" icon, this will bring up a satellite view of your home.
4) Zoom in to the appropriate level you desire.
5) Place your mouse at the point you want to start the measuring process.
6) Right click on the map and select "Measure Distance" from the menu.
7) A small box will appear on the bottom of the page telling you to click on the map to trace the path you want to measure.
8) You can enter as many points as you like. As you go, the distance continues to calculate.
9) If you complete your measurement at the point you started, you will not get a "Total Area" in both sq. ft and sq. meters.
Hope this helps someone out, it did me!