Update docs + email template (#450)

diff --git a/dev/release/README.md b/dev/release/README.md
index 25afab2..5b31083 100644
--- a/dev/release/README.md
+++ b/dev/release/README.md
@@ -129,7 +129,7 @@
 
 ### Pick an Release Candidate (RC) number
 
-Pick numbers in sequential order, with `0` for `rc1`, `1` for `rc1`, etc.
+Pick numbers in sequential order, with `1` for `rc1`, `2` for `rc2`, etc.
 
 ### Create, sign, and upload tarball
 
diff --git a/dev/release/create-tarball.sh b/dev/release/create-tarball.sh
index 9fadedf..2311519 100755
--- a/dev/release/create-tarball.sh
+++ b/dev/release/create-tarball.sh
@@ -73,7 +73,7 @@
 echo "---------------------------------------------------------"
 cat <<MAIL
 To: dev@arrow.apache.org
-Subject: [VOTE][RUST] Release Apache Arrow Rust ${tag}
+Subject: [VOTE][RUST] Release Apache Arrow Rust ${tag} RC${rc}
 
 Hi,