Closed-loop numerical experiments are carried out to analyze the potential accuracies of retrieving the vertical profiles of the spectral coefficient of aerosol extinction (SCAE) from slant-path atmospheric transmittance measurements with the SAGE-III spectrometer launched aboard the Meteor-3M satellite. The SCAE retrieval error depends significantly on the SCAE approximation. The minimum SCAE retrieval errors are achieved by using an aerosol extinction optimal parametrization, which lies in the expansion of variations in the aerosol extinction coefficient into the first few vectors of the quasi-empirical basis. An optimal linear parametrization with four or five parameters is the most promising to interpret remote measurements of slant-path atmospheric transmittance. The advantages of such a parametrization are especially significant when the aerosol extinction coefficients are retrieved in the short-wavelength spectral range. In this range, the errors of retrieval for optimal parametrizations can be several times smaller than those for the Lumpe parametrization. Highly accurate SCAE values retrieved by using the optimal parametrizations can simplify the solution of the subsequent inverse problem of retrieving the microphysical characteristics of stratospheric aerosol.