Effect on the marginalised and unmarginalised errors of changing the step size in the calculation of numerical derivatives with respect to the summed neutrino mass ∑m_ν in the CF/CAMB pipeline. We choose here the case of the spectroscopic probe with optimistic settings, and we stick to the same assumptions and precision parameters as in the rest of the validation Sect. 6. The step sizes (0.1, 0.3, 0.5) are expressed relative to the fiducial value ∑m_ν = 60 meV, and thus correspond to (6 meV, 18 meV, 30 meV).