[css-gaps-1] Fix missing syntax for inset #12848 (#13264)

Author: jav099

css-gaps-1/Overview.bs

@@ -682,7 +682,7 @@ Adjusting gap decoration endpoints: The 'rule-inset' properties</h3>
 
 	<pre class='propdef shorthand'>
 		Name: column-rule-inset, row-rule-inset
-		Value: <<length-percentage>> [ <<length-percentage>> ]?
+		Value: <<length-percentage>> <<length-percentage>>? [/ <<length-percentage>> <<length-percentage>>?]?
 		Applies to: Same as 'column-rule-edge-inset', 'column-rule-interior-inset', 'row-rule-edge-inset', and 'row-rule-interior-inset'
 	</pre>
 
@@ -692,7 +692,11 @@ Adjusting gap decoration endpoints: The 'rule-inset' properties</h3>
 		Applies to: Same as 'column-rule-inset' and 'row-rule-inset'
 	</pre>
 
-	Sets the 'column-rule-inset' and 'row-rule-inset' properties to the same value.
+	Sets the 'column-rule-inset' and 'row-rule-inset' properties to the same value. Syntax is as follows:
+	```
+	edge-start edge-end? [/ interior-start interior-end?]?
+	```
+	where each of ''edge-start'', ''edge-end'', ''interior-start'', and ''interior-end'' are <<length-percentage>> values.
 
 	<pre class='propdef shorthand'>
 		Name: column-rule-inset-start, row-rule-inset-start
@@ -1571,4 +1575,5 @@ Changes since the <a href="https://www.w3.org/TR/2025/WD-css-gaps-1-20250417/">1
 			<a href="https://github.com/w3c/csswg-drafts/issues/12848">Issue 12848</a>,
 			<a href="https://github.com/w3c/csswg-drafts/issues/8402">Issue 8402</a>)
 		<li>Added a paragraph clarifying that gap decorations are not drawn where gaps are suppressed due to fragment breaks.
+		<li>Corrected syntax errors for the inset shorthands.</li>
 	</ul>