Variation in clump size by adopting different filling factors FF in a shell geometry defined with R_min = 49 and R_max = 64 cells. The filling factors used here are FF = 0.07 (circles), FF = 0.13 (diamonds), and FF = 0.23 (triangles). We obtain a mass spectrum ρ(m) ∝ m^-2.04 when adopting FF = 0.23. This is the most consistent with observations of diffuse interstellar clouds. We therefore adopt FF = 0.23 throughout this study.