Schematic illustrating the process used to determine the subhalo's gas mass in grid-based codes. This involves correcting the total gas mass within the subhalo's virial radius by subtracting the host's CGM that is momentarily inside the subhalo's virial radius but not truly associated with it, as described in Section 2.4. The host's CGM mass at the snapshots before and after the subhalo's passage is computed using the average gas density profile, considering a sphere of the subhalo's virial radius during the passage. A comparison between the gas mass obtained using this method and that using bound gas particles in particle-based codes is presented in Figure A.2.