expand navigation summary

systems.tex

@@ -282,7 +282,7 @@ Each day they would accumulate 2 more \glspl{fatigue} in total.
 
 Travelling by road means the troupe can usually sleep in \pgls{village} or at least \pgls{bothy}, so it affords more opportunity for rest.
 
-\makeRule{navigate_land}{Navigating on land}{Intelligence}{Wyldcrafting}{by terrain type}
+\makeRule{navigate_land}{Navigating on land}{Intelligence}{Wyldcrafting}{by terrain type, Failure Margin adds 2 miles}
 \index{Navigation}
 \index{Marching}