\begin{table}%t4
%%\centering

\par
\caption{\label{tab:rginull}Summary of the nulling performance for two survey models and different values of $z_i$.}
\par
\begin{tabular}{ccccccccc}
\hline\hline\noalign{\smallskip}
Survey & $z_i$ & $\sigma_{\rm opt}$ & $r^Q_{\rm GI}(i + 1)$ & $r^Q_{\rm GI}$(mid) & $r^Q_{\rm GI}$(far) & $\Delta_{\rm GG}(i + 1)$ & $\Delta_{\rm GG}$(mid) & $\Delta_{\rm GG}$(far)\\
\hline
S  & 0.53 & 0.280 & $0.1 \times 10^{-4}$ & $1.3 \times 10^{-4}$ & $1.7 \times 10^{-4}$ & 0.01 & 0.19 & 0.22\\
   & 0.76 & 0.255 & $0.4 \times 10^{-4}$ & $1.2 \times 10^{-4}$ & $1.6 \times 10^{-4}$ & 0.01 & 0.11 & 0.15\\
   & 0.96 & 0.235 & $0.3 \times 10^{-4}$ & $0.9 \times 10^{-4}$ & $1.4 \times 10^{-4}$ & 0.00 & 0.05 & 0.07\\
P1 & 0.53 & 0.280 & $7.9 \times 10^{-2}$ & $2.4 \times 10^{-2}$ & $3.2 \times 10^{-2}$ & 0.02 & 0.19 & 0.23\\
   & 0.76 & 0.255 & $4.2 \times 10^{-2}$ & $2.3 \times 10^{-2}$ & $3.0 \times 10^{-2}$ & 0.01 & 0.12 & 0.15\\
   & 0.96 & 0.235 & $2.9 \times 10^{-2}$ & $2.1 \times 10^{-2}$ & $2.8 \times 10^{-2}$ & 0.00 & 0.05 & 0.08\\
   \hline
\end{tabular}
\tablefoot{Given are the median values of the GI over GG ratio of the power spectra $Q^{(ij)}(\ell)$, $r^Q_{\rm GI}$, and the relative deviation of $Q^{(ij)}(\ell)$ from the original power spectra, $\Delta_{\rm GG}$, for the correlation of adjacent bins (``$i\!+\!1$''), the cross-correlation between bin $i$ and the background bin with index $(i+N_z)/2$ (``mid''), and the cross-correlation between bin $i$ and the most distant bin with index $N_z$ at $z \lesssim 2$ (``far''). In addition $\sigma_{\rm opt}$ as determined from $\zeta$ is listed for every case considered.}  \vspace*{2mm}
\end{table}