\documentclass{article}
\usepackage{threeparttable}
\usepackage{multirow}
\usepackage{booktabs}
\usepackage{xcolor}
\begin{document}
\begin{table}[!ht]
\setlength\tabcolsep{0pt}
\centering
\begin{threeparttable}
\begin{tabular}{@{\extracolsep{2ex}}*{2}{lc}}
\toprule
 & \textbf{Total} \\
\midrule
\textbf{value1} &  \\
\hspace{12.0pt}Mean (SD) & 4.5 (2.45) \\
\hspace{12.0pt}Median [Min, Max] & 4.5 [1, 8] \\
\textbf{value2} &  \\
\hspace{12.0pt}a & 3 (37.5\%) \\
\hspace{12.0pt}b & 3 (37.5\%) \\
\hspace{12.0pt}c & 2 (25\%) \\
\textbf{group1} &  \\
\hspace{12.0pt}a & 4 (50\%) \\
\hspace{12.0pt}b & 4 (50\%) \\
\textbf{group3} &  \\
\hspace{12.0pt}c & 4 (50\%) \\
\hspace{12.0pt}d & 4 (50\%) \\
\textbf{group2} &  \\
\hspace{12.0pt}e & 4 (50\%) \\
\hspace{12.0pt}f & 4 (50\%) \\
\bottomrule
\end{tabular}
\end{threeparttable}
\end{table}
\end{document}