Frage Inbed Toolchanger Z-Height

After it broke a new Amana end-mil and Z-height tooll. I'm getting frustrated. So here we go.

After al the manuals from the tool changer installation and communication with support i still have no clue how the machine now knows the z-height.

So in short i have an M1000 with inbed Tool changer included is a Z height switch.

How does it know the Z-Height of the bed. Because it now cuts nicely above the work peace. O apparently cuts in to the stand alone z-height tool as well.

What if i have a bord below the work peace. How does that work. Do you need the separate z-height tool also to test. And how does it do with changes of the tools.

Its al very newbie. But i really cant find the answers.