Solve problem and understanding parameter index.max_region_search

Hello I had my parameter index.max_region_search set on 4. I thought that it means 4 meter radius from my point.
This example shows that maybe I’m wrong

When I have set this param under 8 it can’t find this route. Since index.max_region_search = 8 it can.
Can someone explain why? What I’m doing wrong? Maybe it itsn’t meter as I think?