Top panel: Evolution of the 0.2−2 keV flux, F_X, over time during the high-cadence NICER observations at early times (∼50 days after optical peak). Second panel: spectral hardness estimated as log[A₁/A₂], with A₁ and A₂ the normalisation of the softer and harder blackbody components, respectively. Since smaller log[A₁/A₂] values correspond to harder spectra, J2344 exhibits a harder-when-brighter behaviour. Third and fourth panels: log A₁ and log A₂ in units of L₃₉/[D₁₀(1 + z)]², with L₃₉ the luminosity in 10³⁹ erg s⁻¹ and D₁₀ the distance to the source in units of 10 kpc. Bottom panel: Evolution of the blackbody temperatures for each model component. The kT₁ (orange) and kT₂ (blue) were constrained to the 35−55 eV and 100−140 eV ranges during fitting.