We investigate second-harmonic generation (SHG) from aperiodic optical superlattices in the regime of pump depletion, where the influence of typical fabrication errors which can be introduced by the random -fluctuation of the thickness for each domain in the simulation is considered according to the actual case. It is found that both the SHG conversion efficiencies calculated in undepleted pump approximation (UPA) and an exact -solution decrease when the fluctuation gets larger. However, the decreasing degree is related to the wavelength of the fundamental wave (FW), and the longer the FW wavelength, the lesser the corresponding conversion efficiency reduction. A relative tolerance with respect to SHG conversion efficiency calculated in UPA and exact solution is defined in a previous work, in which a typical model based on the relative tolerance curves is proposed to estimate the SHG conversion efficiency. The simulation results exhibit that the relative tolerance curves are basically coincident with the standard curve when the random fluctuation is very small (typically below 1%). However, as the fluctuation increases, the relative tolerance curves exhibit a large deviation from the standard one, and the deviation is also determined by the wavelength of the FW.