Update ReadBufferFromS3.h

src/IO/ReadBufferFromS3.h

@@ -34,6 +34,7 @@ private:
     UInt64 max_single_read_retries;
 
     /// These variables are atomic because they can be used for `logging only`
+    /// (where it is not important to get consistent result)
     /// from separate thread other than the one which uses the buffer for s3 reading.
     std::atomic<off_t> offset = 0;
     std::atomic<off_t> read_until_position = 0;