Probe-it / any users ?

[dudz]

Ok. I tried a bit of testing via the un licensed version. Seemed to work fine. So Purchased a license this afternoon.
I have calibrated the tip in this program. Now I'm on the surface x,z probing page. I have filed out the inputs on this page to more or less what the example shows to get started. The manual is very informative, but I'm a bit thick. I can see a big learning curve coming on.
First thing that springs to mind is...how do I tell the software how large the material is before executing -x to +x and -y to +y if my zero is in the center of the material ? is this done in a different page on the menu ? or is this not required ?