diff --git a/include/rocksdb/statistics.h b/include/rocksdb/statistics.h
index 56d01aaf3..82405276d 100644
--- a/include/rocksdb/statistics.h
+++ b/include/rocksdb/statistics.h
@@ -74,8 +74,13 @@ enum Tickers : uint32_t {
   NUMBER_KEYS_READ,
   // Number keys updated, if inplace update is enabled
   NUMBER_KEYS_UPDATED,
-  // Bytes written / read
+  // The number of uncompressed bytes issued by DB::Put(), DB::Delete(),
+  // DB::Merge(), and DB::Write().
   BYTES_WRITTEN,
+  // The number of uncompressed bytes read from DB::Get().  It could be
+  // either from memtables, cache, or table files.
+  // For the number of logical bytes read from DB::MultiGet(),
+  // please use NUMBER_MULTIGET_BYTES_READ.
   BYTES_READ,
   NO_FILE_CLOSES,
   NO_FILE_OPENS,