Upper-limit constraints on the dimensionless convergence power spectrum |$\Delta ^{2}_{\delta \kappa }$| and the dimensionless differential-deflection power spectrum |$\Delta ^{2}_{\delta \alpha }$| in the lens galaxy SDSS J0252+0039 for three different subgalactic scales. Each point of the exclusion plot corresponds to a particular subgalactic matter-power-spectrum model |$P_{\delta \psi }(k) \propto \sigma ^2_{\delta \psi } \times k^{-\beta }$|⁠, as specified in Fig. 9. The white contour lines connect models with the same value of |$\Delta ^{2}_{\delta \kappa }$|  (left-hand panel) and |$\Delta ^{2}_{\delta \alpha }$|  (right-hand panel) on a particular scale. Overlaid in black is the 0.99-contour of the exclusion probability. Note that, β represents the power-spectrum slope of the originally investigated potential perturbations |$\delta \psi _{\rm {GRF}}({{\boldsymbol x}})$|⁠. The slopes of the corresponding power spectra of the convergence perturbations |$\delta \kappa _{\rm {GRF}}({{\boldsymbol x}})$| and the deflection perturbations |$\delta \alpha _{\rm {GRF}}({{\boldsymbol x}})$| decrease by 4 and 2, respectively (in terms of the absolute value).