Magnification versus time delay normalization factors for the 12 caustic-crossing galaxies in MACS0416. Each point represents one of the 12 galaxies color-coded by their redshift. Low-redshift arcs normally appear near the center of the cluster, which gives larger Shapiro delays and steeper potentials. That largely explains the larger delays for smaller magnification factors. The x-axis shows the average of the two normalization factors $\langle {\mu }_0\rangle =\left({\mu }_0^{+}+{\mu }_0^{-}\right)/2$ for each arc. The dashed line shows the expected scaling for an isothermal model.