can someone help me?

I would like to know which #s the machine uses for probing.

For example:

When I use the probe i have certain reference planes, which # does the machine use to register these values.
When i use the probe to measure a certain distance which # does the machine use to compare the value of the measurement with that of the reference plane?

In addition, is it possible to make a macro which allows me to make a comparison between 2 grinded surfaces by using the probe?
And it would even be better if the outcome of the measurement can directly effect my offset.

Any advice/information would be great!