Apply suggestions from code review

Co-authored-by: Henrik Tidefelt <henrikt@wolfram.com>

chapters/synchronous.tex

@@ -1045,7 +1045,7 @@ \subsection{Sub-Clock Partitioning}\label{sub-clock-partitioning}
 \end{example}
 
 \begin{example}
-Forbidding systems of equations involving different sub-clocks mean that the following is forbidden:
+Forbidding systems of equations involving different sub-clocks means that the following is forbidden:
 \begin{lstlisting}[language=modelica]
   Real x=sample(time, Clock(1,100));
   Real y;
@@ -1054,7 +1054,7 @@ \subsection{Sub-Clock Partitioning}\label{sub-clock-partitioning}
   z=0;
 \end{lstlisting}
 Here \lstinline!x! and \lstinline!z! are part of one sub-clock partition and \lstinline!y! of another.
-The variables \lstinline!y! and \lstinline!z! are part of a system of equations spanning two sub-clocks, that is not legal.
+The variables \lstinline!y! and \lstinline!z! are part of a system of equations spanning two sub-clocks, which is not allowed.
 
 However, it is not required that the sub-clocks can necessarily be sorted as shown by following legal example:
 \begin{lstlisting}[language=modelica]
@@ -1063,8 +1063,10 @@ \subsection{Sub-Clock Partitioning}\label{sub-clock-partitioning}
   Real z=subSample(y, 2)+x;
 \end{lstlisting}
 Here \lstinline!x! and \lstinline!z! are part of one sub-clock partition, and \lstinline!y! of another.
-The equations can be sorted, but not the sub-clock partitions.
-Note that systems of equations within one sub-clock are also legal.
+The equations form three equation systems with one equation in each (hence trivially satisfying the requirement that only variables from one sub-clock partition are being solved).
+The equation systems need to be solved in a strict order, but the first and last equation system belong to one sub-clock, while the second equation system belongs to another sub-clock.
+This illustrates that there is no guarantee that the sub-clock partitions can be ordered in agreement with the equation systems.
+Note that equation systems with more than one equation are also allowed in sub-clock partitions.
 \end{example}
 
 \subsection{Sub-Clock Inferencing}\label{sub-clock-inferencing}