In the article by S. Hieke, H. Bertz, M. Dettenkofer, M. Schumacher, and J. Beyersmann [Reference Hieke, Bertz, Dettenkofer, Schumacher and Beyersmann1] there was an error in the annotation of the Y-axis in figure 2 (b).
Figures 2 (a) and (b) are reproduced below with the correct annotation.