i forgot about the details, but i remember the help (F1) of TEMS is very detailed about this. They give the method of calculation of C/A and C/I.
i remember that the C/I is not the real C/I though, it’s just an approximation.
C(co)/I > 9dB is needed in order to have good voice quality (above 12dB is even better)
C(adj)/I > -9dB in order to have god voice quality (> -6dB, even better)