How does Technics Overhang Gauge function?

Hi,

Would like to know in detail how the overhang gauge supplied with Technics TTs function and helps in aligning the cartridge.

When I am pushing the cartridge to the gauge its not going through in full because of a elevation at the top of the cartridge.
Do I need to push the cartridge full inside the gauge and then do the alignment?

That 52mm distance recommended - is it after the cartridge goes in fully?

Please help.