[css-anchor-position-1] Make anchor-name a list (#9240)

css-anchor-position-1/Overview.bs

@@ -118,7 +118,7 @@ Creating An Anchor: the 'anchor-name' property {#name}
 
 <pre class=propdef>
 Name: anchor-name
-Value: none | <<dashed-ident>>
+Value: none | <<dashed-ident>>#
 Initial: none
 Inherited: no
 Applies to: all elements that generate a [=principal box=]
@@ -127,18 +127,18 @@ Animation Type: discrete
 
 The 'anchor-name' property declares
 that an element is an <dfn local-lt=anchor>anchor element</dfn>,
-and gives it an <dfn>anchor name</dfn> to be targeted by.
+and gives it a list of <dfn lt="anchor name">anchor names</dfn> to be targeted by.
 Values are defined as follows:
 
 <dl dfn-type=value dfn-for=anchor-name>
 	: <dfn>none</dfn>
 	:: The property has no effect.
 
-	: <dfn><<dashed-ident>></dfn>
+	: <dfn><<dashed-ident>>#</dfn>
 	:: If the element generates a [=principal box=],
 		the element is an [=anchor element=],
-		with an [=anchor name=] equal to the <<dashed-ident>>.
-		The [=anchor name=] is a [=tree-scoped name=].
+		with a list of [=anchor names=] as specified.
+		Each [=anchor name=] is a [=tree-scoped name=].
 
 		Otherwise, the property has no effect.
 </dl>