As a standard practice in quantum chemistry, typical numerical convergence thresholds are tight enough to not affect the resulting accuracy. For example, Q-Chem's default CCSD convergence criteria are 10 -6 hartree for energies and 10 -4 for amplitudes; 26 Molpro uses 10 -6 hartree for energies and 10 -5 for amplitudes. 27 Some packages use a single threshold, for example, GAMESS uses 10 -7 for amplitudes and ORCA uses 10 -5 -10 -6 hartree for energies. Thus, it appears that 7 decimal digits is sufficient for correlation energy (we note that 10 -7 hartree is three orders of magnitude tighter that chemical accuracy).