True mass-observed richness relation for the clusters at redshift z = 0.22 as measured in both hydro-runs. The solid lines show the linear regression model results, with the shaded region indicating the 1σ uncertainty on the intercept and slope parameters. In each sub-figure, the right sub-panel shows the probability distribution function of the λ_obs with respect to the corresponding best-fit linear model, with the shaded regions marking the corresponding scatter σ_{log λobs}. The dotted black lines exhibit the model for the richness weak-lensing mass relation, as described in the last section.