documentclass[10pt]{llncs}
usepackage{graphicx}
usepackage{sistyle}
SIthousandsep{,}
usepackage{booktabs}
usepackage{array, makecell}
usepackage{adjustbox}

begin{document}
title{Test}
maketitle

begin{table*}[!tp]
    centering
    caption{Summary}
    label{tab:inspection}
    begin{adjustbox}{max width=textwidth}
        begin{tabular}{lrrr}
            toprule
            & multicolumn{3}{c}{thead{Row}} \
            cline{2-4}
            & texttt{Col #1} & texttt{Col #2}   & texttt{Col #3} \
            midrule
            Feature #1
            & num{55555}              & num{222222}           & num{1111111} \
            midrule
            quad Feature #2
            & num{44444} (22.11%)    & num{222222} (11.11%) & num{1111111} (44.44%) \
            midrule
            quad quad Feature #3
            & num{44444} (55.55%)    & num{222222} (33.33%) & num{1111111} (22.22%)\
            quad quad quad Feature #4
            & num{33333} (55.55%)    & num{66666} (22.22%)  & num{1111111} (100%) \
            bottomrule
        end{tabular}
    end{adjustbox}
    vspace{-10pt}
end{table*}


end{document}