diff --git a/google/pubsub/v1/pubsub.proto b/google/pubsub/v1/pubsub.proto
index 832e0649..a42d0322 100644
--- a/google/pubsub/v1/pubsub.proto
+++ b/google/pubsub/v1/pubsub.proto
@@ -839,8 +839,11 @@ message ReceivedMessage {
   // The message.
   PubsubMessage message = 2;
 
-  // Delivery attempt counter is 1 + (the sum of number of NACKs and number of
-  // ack_deadline exceeds) for this message.
+  // The approximate number of times that Cloud Pub/Sub has attempted to deliver
+  // the associated message to a subscriber.
+  //
+  // More precisely, this is 1 + (number of NACKs) +
+  // (number of ack_deadline exceeds) for this message.
   //
   // A NACK is any call to ModifyAckDeadline with a 0 deadline. An ack_deadline
   // exceeds event is whenever a message is not acknowledged within
@@ -848,13 +851,10 @@ message ReceivedMessage {
   // Subscription.ackDeadlineSeconds, but may get extended automatically by
   // the client library.
   //
-  // The first delivery of a given message will have this value as 1. The value
-  // is calculated at best effort and is approximate.
+  // Upon the first delivery of a given message, `delivery_attempt` will have a
+  // value of 1. The value is calculated at best effort and is approximate.
   //
   // If a DeadLetterPolicy is not set on the subscription, this will be 0.
-  // <b>EXPERIMENTAL:</b> This feature is part of a closed alpha release. This
-  // API might be changed in backward-incompatible ways and is not recommended
-  // for production use. It is not subject to any SLA or deprecation policy.
   int32 delivery_attempt = 3;
 }