Posteriors on cosmological and nuisance parameters, using the analytical forward model and the Fisher analysis, with explicit scaling relations. We observe that many pairs of parameters are degenerate (elongated contours), denoting the ill-parametrisation of this model. The simulation-based forward model does not show this behaviour in Figure 11. XODs are produced from 200 deg² X-ray surveys, selecting clusters with the flux cut CR_lim = 0.02c/s.