Use item list instead of \textbf for the only 'Proposition' there is

chapters/classes.tex

@@ -1104,12 +1104,10 @@ \section{Balanced Models}\doublelabel{balanced-models}
   \end{nonnormative}
 \end{itemize}
 
-Based on these restrictions, the following strong guarantee can be given
-for simulation models and blocks:
-
-\textbf{Proposition 1:}
-
-All simulation models and blocks are globally balanced.
+Based on these restrictions, the following strong guarantee can be given:
+\begin{itemize}
+\item All simulation models and blocks are globally balanced.
+\end{itemize}
 
 \begin{nonnormative}
 Therefore the number of unknowns equal to the number of equations of a simulation model or block, provided that every used