Luminosity constraints from the energy-balance calculations for ZTF0038B (horizontal lines) are compared with field brown dwarf evolutionary tracks (solid blue and green curves). The shaded regions around the evolutionary tracks indicate the uncertainties in the evolutionary models based on the mass uncertainty from J. van Roestel et al. (2021). The horizontal dashed lines indicate the age constraints from this work and M. Zorotovic & M. Schreiber (2022). Assuming the mass presented in J. van Roestel et al. (2021), we provide a nominal age estimate, highlighted in yellow.