Clarify displayUnit for %par

Closes #2339

chapters/annotations.tex

@@ -822,7 +822,10 @@ \subsubsection{Text}\doublelabel{text}
 \begin{itemize}
 \item
   \%\emph{par} and \%\{\emph{par\}} replaced by the value of the
-  parameter \emph{par}. The intent is that the text is easily readable,
+  parameter \emph{par}. 
+  If the value is numeric, tools shall display the value with displayUnit, formatted according to bipm-specification.
+  E.g., for \lstinline!parameter Real t(unit="s",displayUnit="ms")=0.1! tools shall display \lstinline!100 ms!.
+  The intent is that the text is easily readable,
   thus if par is of an enumeration type, replace \%par by the item name,
   not by the full name.\\
   \emph{{[}Example: if par="Modelica.Blocks.Types.Enumeration.Periodic",