add md issue

files/en-us/web/html/element/summary/index.md

@@ -27,7 +27,7 @@ The content of the `<details>` provides the {{glossary("accessible description")
 
 If a `<details>` element's first child is not a `<summary>` element, the {{Glossary("user agent")}} will use a default string (typically "Details") as the label for the disclosure box.
 
-### Default style
+##### Default style
 
 Per the HTML specification, the default style for `<summary>` elements includes `display: list-item`. This makes it possible to change or remove the icon displayed as the disclosure widget next to the label from the default, which is typically a triangle.