Calculated change in source number density in the different tomographic bins of KiDS-1000 for an NFW halo of mass M_500c = 2 × 10¹⁴ M_⊙, z_cl = 0.2. In the low-redshift tomographic bins the increase in observed sky area (leading to a dilution of the source number density) dominates over the source number density increase due to fainter galaxies which move into the sample, whereas the opposite is the case for the high-redshift tomographic bins.