%%
%% The LaTeX Companion, 3ed
%%
%% Example 3-3-36 on page I-176 in "Customizing units and quantities".
%%
%% 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{135.0pt}
\setlength\parindent{0pt}
%StartShownPreambleCommands
\usepackage{siunitx}
\newcommand\sample[1]{#1: \qty{12.3(4)}{\km}\\[5pt]}
%StopShownPreambleCommands

\begin{document}
                                            \sample{A}
\sisetup{separate-uncertainty}              \sample{B}
\sisetup{separate-uncertainty-units=repeat} \sample{C}
\sisetup{separate-uncertainty-units=bracket}\sample{D}
\sisetup{separate-uncertainty-units=single} \sample{E}
\end{document}