Magnitude distribution of the counterpart vs. the X-ray flux for sources with CTP_quality> = 2 (left) and CTP_quality< 2 (right). A cut at log ML_FLUX_s > −20 has been applied. The magnitude distribution is clearly different. The green lines represent the median 0.5–2 keV flux (−13.99 and −14.17), while the red lines mark the 90th percentile of the r-band magnitude distribution (22.88 and 24.13).