diff --git a/README.md b/README.md
index c498142..9ee7afc 100644
--- a/README.md
+++ b/README.md
@@ -17,7 +17,7 @@ if __name__ == '__main__':
 List
 ----
 ```python
-<list> = <list>[from_inclusive : to_exclusive : step_size]
+<list> = <list>[from_inclusive : to_exclusive : ±step_size]
 ```
 
 ```python