Halo mass function for the LR (solid purple lines) and the HR simulation (solid orange lines). The mass function of the LR simulation is within 10% of HR simulation for LR haloes greater than 40 particles as can be seen from the solid purple line in the bottom panel. The black dashed line corresponds to the LR haloes after correcting their masses with the HR counterparts with a simple 1-1 matching. After the 1-1 matching, and training with RF, the LR halo number density still drops compared to the HR, for haloes with fewer than 40 particles.