Demonstration of the necessity of an energy scale correction. Shown in black are the total spectra of calibration observations between revolutions of 1000 and 1500 (<7 keV) and the total spectra of calibration observations plus stacked observations in the same time period (>7 keV), outside the Cu hole region. The count axis for data >7 keV has an arbitrary scaling. Top panel: models and data, while the bottom panel shows their ratio. There are two “6-line” models. One (blue) assumes that the lines are at their standard energies. The other (pink) has a linear compression model for the line energies about Cu-Kα where δE/E = 0.0013 keV⁻¹. The poorly-modelled line wings do not affect the best-fitting compression factors.