Cumulative number counts of galaxy clusters in the 0.5–2 keV band from the Swift survey (red squares) as compared to results from the XMM-COSMOS, ROSAT, and CDF-S surveys (black triangles and the black solid line). The red dotted line shows the broken power-law fit to the Swift data only, and the blue dashed line shows the fit to the combined data with fluxes lower than ﹩4\times {{10}^{-12}}﹩ erg cm⁻² s⁻¹.