diff --git a/40.md b/40.md
index f3fabd4..6c5ecf4 100644
--- a/40.md
+++ b/40.md
@@ -13,7 +13,7 @@ The `expiration` tag enables users to specify a timestamp at which the message s
 ```
 tag: expiration
 options:
- - [timestamp]: required
+ - [UNIX timestamp in seconds]: required
 ```
 
 #### Example