Distribution of GNN predicted masses, ${\text{M}}_{500}^{\text{GNN}}$, vs. true cluster masses, ${\text{M}}_{500}^{\text{True}}$, for the training (left) and testing (right) samples of sizes 9305 and 1950, respectively. The black line represents a 1-to-1 relation. The bottom panel in both panels shows the fractional residual distribution; the solid blue lines and shaded regions represent the median and 1σ dispersion, respectively. We find a 1σ dispersion of about 7% and 6% for the testing and training samples, respectively.