diff --git a/13.md b/13.md
index 2c60929c..360bde6c 100644
--- a/13.md
+++ b/13.md
@@ -18,7 +18,7 @@ Mining
 To generate PoW for a `NIP-01` note, a `nonce` tag is used:
 
 ```json
-{"content": "It's just me mining my own business", "tags": [["nonce", "1", "20"]]}
+{"content": "It's just me mining my own business", "tags": [["nonce", "1", "21"]]}
 ```
 
 When mining, the second entry to the nonce tag is updated, and then the id is recalculated (see [NIP-01](./01.md)). If the id has the desired number of leading zero bits, the note has been mined. It is recommended to update the `created_at` as well during this process.