Top: the νF(ν) spectra for region I best fit by a COMP model (left), the νF(ν) spectra for region II best fit by a COMP+BB model (middle), and the νF(ν) spectra for subregion IVc best fit by a Band+PL model (right). Bottom: average examples of counts spectrum plots during the Fermi-GBM BTI region of subinterval IVb (Left: t 0 + 243.1 s; middle: t 0 + 244.1 s; and right: t 0 + 265.6 s) achieved by using the PPU-correction method described in Section 3.1. The spike at 511 keV is ignored during the fitting process and does not affect the fit statistic.