如何调整 longtable 中的缩进？

Question

我想在以下长表中调整表格的缩进：

\documentclass{article}
\usepackage{longtable}
 \usepackage[none]{hyphenat}

\begin{document}
    \centering
    \setlength{\arrayrulewidth}{0.2mm}
    \setlength{\tabcolsep}{18pt}
    \renewcommand{\arraystretch}{1.3}
    \small
    \begin{longtable}{|@{\hspace*{\leftmargin}}p{2cm}|p{2.8cm}|p{2.8cm}|p{2.8cm}|}
        \caption{Summary of decomposition techniques executed on the EEG signals and their significant results}\label{tab:summary}\\
        \hline
        \textbf{Ordering techniques} &  \textbf{Real-world applications}    &   \textbf{Advantages} & \textbf{Limitations} \\
        \hline
        \endfirsthead
        \multicolumn{4}{c}%
        {\tablename\ \thetable\ -- \textit{Continued from previous page}} \\
        \hline
        \textbf{Ordering techniques} &  \textbf{Real-world applications}    &   \textbf{Advantages} & \textbf{Limitations} \\
        \hline
        \endhead
        \hline \multicolumn{4}{r}{\textit{Continued on next page}} \\
        \endfoot
        \hline
        \endlastfoot
    \end{longtable} 
\end{document}

生成下表：

如何调整表格中的缩进（红色方块）？