Dynamic range correction for spectrum analyzer

Using a spetrum anzlyzer to measure DUT nonlinearity distortions, the measurement uncertainty depends on the amplitude and phase of the spectrum analyzer's internal distortion products (if not consider signal source nonlinearity distortions products) . If we want no more than 1dB of uncertainty in measurement , we must be sure the internal distortion product is at least 19dB below the distortion products that we wish to measure. So the dynamic range of spectrum analyzer is reduced by 9.5dB for second order and 6.3dB for third order. Is my conclusion right?