Since the original file is unlicensed, I'm unable to send an edited version. However, I can share a snippet of code shared by MJSU sometime ago. It's not tested, so I'm unsure if this makes it any better. The real issue is how the zoom level of maps fluctuates, so accurately calculating grids is a bit touchy now of days.
private string GetGridPosition(Vector3 pos)
const float gridCellSize = 146.3f;
int maxGridSize = Mathf.FloorToInt(World.Size / gridCellSize) - 1;
float halfWorldSize = World.Size / 2f;
int xGrid = Mathf.Clamp(Mathf.FloorToInt((pos.x + halfWorldSize) / gr