Top: fit of the SCUBA-2 MAMMOTH-1 true differential number counts at 850 μm using the functions given in literature works for blank fields (Chen et al. 2013b; Casey et al. 2013; Zavala et al. 2017; Geach et al. 2017) with N₀ free to vary. Bottom: SCUBA-2 MAMMOTH-1 true cumulative number counts at 850 μm compared to the fit models obtained in the top panel. In both panels, the blue dot-dashed curve is our true number counts curve from Table 4. All the literature models need a significant increase of their normalization parameter N₀ to fit our data at 850 μm, revealing that the covered effective area is overdense with respect to blank fields. We list the values in Table 6.