Header overlaps in table

Question

Why is the header overlaps in the following table: and how can I improve it?

\begin{table}[H]
        \centering
        \sisetup{table-format=1.3e-2, table-alignment=center, tight-spacing}
        \setlength{\tabcolsep}{3pt}
        \small
        \centering

        \sisetup{detect-weight,mode=text}
        \renewrobustcmd{\bfseries}{\fontseries{b}\selectfont}
        \renewrobustcmd{\boldmath}{}
        % abbreviation
        \newrobustcmd{\B}{\bfseries}
        % shorten the intercolumn spaces
        \addtolength{\tabcolsep}{-4.1pt}

        \begin{tabularx}{\linewidth}{X cSS[table-format=1.5] SS[table-format=1.5]}
            \toprule
            \thead {Algorithm\\ Name}  & {\thead{ABC Dataset \\ Name} }& {\thead{Bxxx ABS Txx\\ aaaa $80\%$ }} & {\thead{Mxxx YYYYYYY Tcxx\\ Tzzz $80\%$} }
            & {\thead{Bxxx sdsdf Tfds\\Tdfs $90\%$}} \\ [0.5ex]
            \midrule
            ABCD & XXXXX YYY & 0.222 & 0.228 & \B 0.230 \\
            ABCD & DEFG       & 0.222 & \B 0.282 & 0.222 \\
            ABCD & ABCD       & 0.992 & 0.992 & \B 0.998 \\
            ABCD & XXXXX Y    & 0.992 & 0.992 & \B 0.992 \\ 
            DEF  & XXXXX Hand & 0.220 & \B 0.222 & 0.222 \\
            DEF  & DEFG       & 0.223 & 0.232 & \B 0.22 \\
            DEF  & ABCD       & 0.999 & \B 2.000 & 0.999 \\
            DEF  & XXXXX YY   & 0.998 & \B 0.999 & 0.998 \\ [2ex]
            \bottomrule
        \end{tabularx}
        \caption{Cfdfsd (In \textbf{Bold} the gsfdsd per line)}
    \label{table:4}
    \end{table}

Answer 1

i suspect that you like to have your table like this:

it is based on my answer to your previous question

\documentclass{article}
\usepackage{booktabs, makecell}
\usepackage{siunitx}

\usepackage{etoolbox}%  <---
\newcommand{\B}{\fontseries{b}\selectfont} %  <---
\robustify\B%  <---

\begin{document}
    \begin{table}
    \centering
\sisetup{detect-weight} %  <---
    \centering
\begin{tabular}{l c *{3}{S[table-format=1.3]}} %  <---
    \toprule
\thead{Algorithm\\ Name}
     & \thead{ABC Dataset \\ Name} 
                        & {\thead{Bxxx ABS Txx \\ 
                                 aaaa \SI{80}{\%} }} 
                                & {\thead{Mxxx YYYYYYY\\ 
                                          Tcxx Tzzz \SI{80}{\%} }}
                                            & {\thead{Bxxx sdsdf Tfds \\
                                                      Tdfs \SI{90}{\%}}}
                                                        \\                                               
     \midrule
    ABCD & XXXXX YYY    & 0.222 &    0.228 & \B 0.230 \\
    ABCD & DEFG         & 0.222 & \B 0.282 &    0.222 \\
    ABCD & ABCD         & 0.992 &    0.992 & \B 0.998 \\
    ABCD & XXXXX Y      & 0.992 &    0.992 & \B 0.992 \\
    DEF  & XXXXX Hand   & 0.220 & \B 0.222 &    0.222 \\
    DEF  & DEFG         & 0.223 &    0.232 & \B 0.22  \\
    DEF  & ABCD         & 0.999 & \B 2.000 &    0.999 \\
    DEF  & XXXXX YY     & 0.998 & \B 0.999 &    0.998 \\
    \bottomrule
    \end{tabular}
    \caption{11 my caption}
\label{table:3}
    \end{table}
\end{document}

Note:

• always provide complete small document, which we can copy and compile in our computers. for example, your code snippet doesn't provide important information from preamble or you have them on the wrong place in document
• if you have follow-up question (as your question is), please provide link to previous one
• if you accept answer from your previous question, please use it in your similar table design

edit: sorry, in the first version of answer in rash i didn't consider your table body, now i correct this now. with it you have some new issues:

• table is significantly wider as in your previous question
• for column headers are used theads from makecell package (similar as Bernard do in his answer) since you use siunitx package you should use it in seting percentages values.

Answer 2

Your S columns have inconsistent table-format: by default you have a format in scientific notation, some in the table have 5 decimal digits, but you actually have 3. Also you have one unused S column. Also, it would be better to set the 2nd column as a X column.

Here's the code I propose:

\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage{siunitx}
\usepackage{etoolbox}
\usepackage{tabularx, booktabs, makecell} %

\begin{document}

\begin{table}[!htb]
    \centering
    \sisetup{table-format=1.3, table-number-alignment=center, tight-spacing,}% table-column-width =2.5cm 
    \setlength{\tabcolsep}{3pt}
    \small
    \centering

    \sisetup{detect-weight,mode=text}
    \renewrobustcmd{\bfseries}{\fontseries{b}\selectfont}
    \renewrobustcmd{\boldmath}{}
    % abbreviation
    \newrobustcmd{\B}{\bfseries}
    % shorten the intercolumn spaces
    \setlength{\tabcolsep}{4pt}

    \begin{tabularx}{\linewidth}{l>{\centering}XSSS}
        \toprule
        \thead {Algorithm\\ Name} & {\thead{ABC Dataset \\ Name} }& {\thead{Bxxx ABS Txx \\ aaaa $80\%$ }} & {\thead{Mxxx YYYYYYY\\ Tcxx Tzzz $80\%$} }
        & {\thead{Bxxx sdsdf Tfds \\Tdfs $90\%$}} \\ [0.5ex]
        \midrule
        ABCD & XXXXX YYY & 0.222 & 0.228 & \B 0.230 \\
        ABCD & DEFG & 0.222 & \B 0.282 & 0.222 \\
        ABCD & ABCD & 0.992 & 0.992 & \B 0.998 \\
        ABCD & XXXXX Y & 0.992 & 0.992 & \B 0.992 \\
        DEF & XXXXX Hand & 0.220 & \B 0.222 & 0.222 \\
        DEF & DEFG & 0.223 & 0.232 & \B 0.22 \\
        DEF & ABCD & 0.999 & \B 2.000 & 0.999 \\
        DEF & XXXXX YY & 0.998 & \B 0.999 & 0.998 \\ [2ex]
        \bottomrule
    \end{tabularx}
\end{table}

\end{document}