Update explainer.md

Author: Jihye Hong

explainer.md

@@ -58,10 +58,10 @@ The following properties are proposed to embrace the developer’s intention and
       - Let the upper edge of the C is positioned `250px` down from the upper edge of the E and the leftside edge of the C is positioned `200px` to the right from the leftside edge of the E.
       - Let the upper edge of the D is positioned `100px` down from the upper edge of the E and the leftside edge of the D is positioned `500px` to the right from the leftside edge of the E.
       - Let the initial focus goes to A among the DOM subtree rooted at E.
-      - `nav-rule: projection` is applied to the element E and the current focused element is A, the focus moves to D when there is an input from the right-arrow key.
-      - `nav-rule: direction` is applied to the element E and the current focused element is A, the focus moves to C when there is an input from the right-arrow key.
-      - `nav-rule: nearest` is applied to the element E and the current focused element is A, the focus moves to B when there is an input from the right-arrow key.
-      
+      - If the current focused element is A and there is an input from the right-arrow key,
+        - If `nav-rule: projection` is applied to the element E, the focus moves to D.
+        - If `nav-rule: direction` is applied to the element E, the focus moves to C.
+        - Otherwise `nav-rule: nearest` is applied to the element E, the focus moves to B.
 
   - nav-loop property (CSSUI4)