\begin{table}%t7 \caption{\label{dindex}Inferred metallicity, $N_{\rm HI}$ and $D$-index of Mg~{\sc ii} systems with $W_{\rm r}>1.0$~\AA ~ in the UVES sample.} %\centerline { \begin{tabular}{l c c c c} \hline\hline\noalign{\smallskip} GRB & $z_{\rm abs}$ & [X/H]$^a$ & $N_{\rm HI}({\rm cm}^{-2})^a$ &$D$-index$^b$\\ \hline 021004& 1.380 &$-0.63$& 20.3&$8.32\pm0.22$ \\[0.5ex] 021004& 1.603 &$-0.65$&20.8& $9.99\pm0.47$ \\[0.5ex] 050820A& 0.692 & & &$9.0\pm0.03^c$ \\[0.5ex] 050820A& 1.429 &$-0.34$& $>$$19.2$ &$8.13\pm0.22$ \\[0.5ex] 060418& 0.603 &$-1.13$& $>$$22.0$&$10.39\pm0.09^d$ \\[0.5ex] 060418& 0.656 &$-0.77$&$>$$19.2$ &$7.51\pm0.05$\\[0.5ex] 060418& 1.107 &$-0.85$&21.1 &$8.17\pm0.06$ \\[0.5ex] 060607A& 1.803 &$-0.21$& 19.0&$9.12\pm0.06$ \\[0.5ex] 080319B& 0.715 &$-0.17$& $>$$18.7$&$8.06\pm0.01$ \\[0.5ex] \hline \end{tabular}} \par \medskip $^a$ Metallicities and $N_{\rm HI}$ values inferred using the relation by \cite{Ledoux2006a}; $^b$ {\it D}-index calculated using Eq.~\ref{eqd}, following the method recommended by \cite{Ellison2009}; $^c$ {\it D}-index calculated without including the iron column density term (see \citealt{Ellison2009}); $^d$ iron lines are saturated. The {\it D}-index calculated without including the iron column density term would be $D=9.48\pm0.08$; \end{table}