diff --git a/src/js/client.js b/src/js/client.js
index 97f04481e..d7024bba5 100644
--- a/src/js/client.js
+++ b/src/js/client.js
@@ -1230,6 +1230,7 @@ angular.module('Application').service('Client', ['$http', '$interval', 'md5', 'N
             if (error) return callback(error);
             if (status !== 200) return callback(new ClientError(status, data));
 
+            // the datapoint returned here is an [value, timestamp]
             callback(null, data);
         });
     };