I displayed the 700 sites provided in
ground_measures_*_feature.csv as you did (triangles), but also the 18,130 cells from
grid_cells.geojson (small dots). The problem appears with the latter file.
submission_format.csv file there are 9,066 cells. Looking at the locations of these cells (red dots below, as opposed to the blue dots and the 700 sites), we can see a large concentration of these cells are in California and Colorado. Is it normal that the metric of the challenge favor these 2 states ? This question linked to Problem clarification thread and how the test data will look like