I've kinda of understood now, thank you.
But I still find it quite complicated: wouldn't it be easier if it was said that, as a starting point for example, the depth for one click is 1024?

In this way it would be easier to calculate more or less deep depths. In fact in my level I also have a slim tilt1 bridge (about an half click): setting 512 was perfect for its depth. And, as I repeat, 4096 was perfect for a 1x1 sector cube.