An interesting question, I assume you wanted to know the distance the probe moved moves before triggering?
I've measured it by running the probe calibration, lowering the probe (using the provided buttons in the window that pops up), until contact with the bed, I then placed several 0.01 mm shims under the hot-end until the led came on. Basically, I measured a distance between 0.05 and 0.06mm (constantly), the point the led lights indicating contact/triggering...
Not sure if this is what you wanted to know but it was a worthwhile exercise anyway...
I would also argue if you know this distance, you should be able to set the offset automatically relative to the bed.