%%
%% The LaTeX Companion, 3ed
%%
%% Example 7-4-14 on page I-556 in "Customizing the subcaptions".
%%
%% Copyright (C) 2022 Frank Mittelbach
%%
%% It may be distributed and/or modified under the conditions
%% of the LaTeX Project Public License, either version 1.3c
%% of this license or (at your option) any later version.
%%
%% See https://www.latex-project.org/lppl.txt for details.
%%

\documentclass{tlc3exa}
\pagestyle{empty}
\setcounter{page}{6}
\setlength\textwidth{123.0pt}

  \setlength\textheight{20\baselineskip}

%StartShownPreambleCommands
\usepackage{graphicx}
\usepackage[font={sl,small}]{subcaption}
\captionsetup[table]{position=top,skip=3pt}
\captionsetup[subtable]{singlelinecheck=false,skip=0pt,
                        format=hang,justification=raggedright}
\DeclareCaptionSubType*[arabic]{table}
\newcommand\TAB[2]{\fbox{\parbox{#2\textwidth}{Table #1}}}
%StopShownPreambleCommands

\begin{document}
\begin{figure}[!t]
  \subcaptionbox{An image}{\fbox{No elephant around}}\hfill
  \subcaptionbox{Very lonely cat\label{f2}}
                [13mm]{\includegraphics{cat}}
  \caption{Two subfigures}
\end{figure}
There is a cat in subfigure \ref{f2} but no elephant.
\begin{table}[!b]
  \caption{Three subtables}\label{tbl}
    \subcaptionbox{First\label{t1}}{\TAB{1}{.4}}\hfill
    \subcaptionbox{Second}         {\TAB{2}{.4}}
  \par\medskip
    \subcaptionbox{Third table with a much longer
                   caption\label{t3}}{\TAB{3}{.8}}
\end{table}
Table~\ref{tbl} contains subtables~\ref{t1} to~\ref{t3}.
\end{document}