[css-anchor-position][editorial] Add note.

Author: tabatkins

css-anchor-position-1/Overview.bs

@@ -1167,9 +1167,19 @@ this property determines which [=position option=] to use.
 		that didn't result in overflow,
 		use that option.
 
+		Note: In other words, if all of the options cause the element to overflow,
+		then by default
+		the element will stay with the last successful [=position option=] it found
+		that <em>didn't</em> cause overflow,
+		keeping its position reasonably stable.
+		With ''always'' specified, however,
+		it will instead use the specified strategy
+		to select the "fallback" [=position overflow=],
+		regardless of what was previously successful.
+
 	: <dfn>hide</dfn>
 	::
-		Use the first option (as for ''first''),
+		Use the first [=position option=] (as for ''first''),
 		but also hide the box such that it (and all of its contents)
 		are invisible (like ''visibility: hidden'')
 		and do not contribute to [=scrollable overflow=].