Only one third of the nucleons in $^{208}$Pb occupy the saturation density area. Consequently nuclear observables related to average properties of nuclei, such as masses or radii, constrain the equation of state (EOS) not at saturation density but rather around the so-called crossing density, localised close to the mean value of the nuclei density: $\rho\simeq$0.11 fm$^{-3}$. This provides an explanation for the empirical fact that several EOS quantities calculated with various functionnals cross at a density significantly lower than the saturation one. The third derivative M of the energy at the crossing density is constrained by the giant monopole resonance (GMR) measurements in isotopic chain rather than the incompressibility at saturation density. The Pb and Sn GMR measurements provide M=1110 $\pm$ 50 MeV (5% uncertainty), which extrapolation gives K$_\infty$=230 $\pm$ 40 MeV (17% uncertainty).