Many FFT implementations return the magnitude spectrum which is not normalized. Our FFT returns the complex amplitudes which is the magnitude spectrum multiplied with 1/N. You can decide where you do the normalization – on the FFT or on the inverse. We do it on the FFT because then the complex spectrum returned directly corresponds to the amplitudes an phases of the sinusoids used to reconstruct the time signal.
y_k = 1/N Sum([j=0 to N-1] x_j * Exp(-2*Pi*i*j*k/N)
x_j = Sum([k=0 to N-1] y_k * Exp(2*Pi*i*j*k/N)
If you install the Spectral Analysis Option for FlexPro then you have an exact-n FFT available, which returns the magnitude spectrum instead of the complex amplitudes.