What about it is "wrong"? Perhaps I'm scarred by my own institution's predilection of left-justifying (or center) columns of numbers that this seems fine to me.
To see the difference, typeset this with LaTeX:
\documentclass{standalone}
\begin{document}
-50 vs $-50$
\end{document}-Lorem ipsum dolor sit amet
+Lorem ipsum dolor sit amet
−Lorem ipsum dolor sit amet