r' -> t'

Just looks like a type-o

pdf/grandpa.tex

@@ -358,7 +358,7 @@ Let's define $V_{r,v,t}$ be the set $V_{r,v}$ at time $t$ and similarly for $C_{
 
 \begin{lemma} \label{lem:message-monotonicity-completed-estimate}
 Let $v,v'$ be (possibly identical) honest participants, $t,t'$ be times with $t \leq t'$, and $r$ be a round.
-Then if $V_{r,v,t} \subseteq V_{r,v',r'}$ and $C_{r,v,t} \subseteq C_{r,v',r'}$, all these sets are tolerant, and $v$ sees that $r$ is completable at time $t$, then $E_{r,v,t} \leq E_{r,v',t'}$ and $v'$ sees that $r$ is completable at time $t'$.
+Then if $V_{r,v,t} \subseteq V_{r,v',t'}$ and $C_{r,v,t} \subseteq C_{r,v',t'}$, all these sets are tolerant, and $v$ sees that $r$ is completable at time $t$, then $E_{r,v,t} \leq E_{r,v',t'}$ and $v'$ sees that $r$ is completable at time $t'$.
 \end{lemma}
 
 \begin{proof} Since $v$ sees that $r$ is completable at time $t$, $V_{r,v,t}$, $C_{r,v,t}$ each contain votes from $n-f$ voters and so the same holds for $V_{r,v',t'}$ and $C_{r,v',t'}$.