The oscillator strengths and TPA cross-sections associated with the lowest excited state in the randomly selected single configurations of the PNP and NR systems are presented in tion energies. We include the effective external field in our calculations because it has been shown to yield accurate absorption intensities comparable to those for enlarged quantum subsystems. From the results in Figure and 19, it is evident that large cutoff distances are needed to converge the oscillator strengths and TPA cross-sections. In fact, it appears that the simulation boxes are not large enough, except in the case of PNP1 and NR-in-BLG. This emphasizes the importance of an accurate description of the polarization throughout the system where convergence with respect to the box size is expected to be faster, in particular when the effective external field effects are included. because the errors are almost exclusively positive, which can be attributed to the effective external field effects. In relative terms, not considering the outliers, the average errors are about 3-12 % for the oscillator strengths and 4-7 % for the TPA cross-sections.