[css-anchor-1] Stop implying that an element can have multiple implicit anchor elements.

Author: tabatkins

css-anchor-1/Overview.bs

@@ -316,8 +316,8 @@ might not be capable of anchoring the positioned element.
 	which satisfies the following conditions:
 
 	* If |name| is not provided,
-		but |query el| has one or more [=implicit anchor elements=],
-		|el| is one of those elements.
+		but |query el| has an [=implicit anchor element=],
+		|el| is that element.
 	* If |name| is provided,
 		|el| is an [=anchor element=] with an [=anchor name=] of |name|.
 	* Either |el| is a descendant of |query el|'s [=containing block=],
@@ -343,14 +343,18 @@ might not be capable of anchoring the positioned element.
 	in anchor positioning.
 </div>
 
-An element can have one or more <dfn export>implicit anchor elements</dfn>,
-defined by other features.
-This specification does not define any [=implicit anchor elements=] itself.
+An element can also have an <dfn export>implicit anchor element</dfn>,
+used when an [=anchor function=] doesn't specify an explicit [=anchor name=].
 
 Note: The Popup API, for example,
 defines an [=implicit anchor element=] for a popup--
 the element that the popup is attached to.
 
+Note: An element can have only one implicit anchor element.
+If we end up with multiple features defining
+potentially different [=implicit anchor elements=] on the same element,
+this specification will define a resolution order.
+
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