Fraction of simulated spatially correlated clusters that are rejected by applying the cut on ℱ(t) optimised in order to ensure FAR of one per century, one per year, one per month, one per week, one per day, or one per hour from Poisson-distributed background (with r_bkg = 0.05 s⁻¹), as a function of injected multiplicity of the cluster. The solid lines (resp. dashed lines) show the results without (resp. with) the spatial penalty term in Eq. (15).