Fermi/GBM observed inverse cumulative distribution of 64-ms-binned photon fluxes in the 10-1000 keV band (blue solid line, with the grey band showing the 90% confidence band due to Poisson and measurement uncertainties), compared with our best-fitting model, Eq. B.4, with α = 2.25 and ph cm⁻² s⁻¹ (red dashed line). The slight excess over the expected trend at high fluxes is likely due to contamination of the sample by magnetar giant flares in local galaxies (Burns et al. 2021).