diff --git a/css-nav-1/Overview.bs b/css-nav-1/Overview.bs
index dac9939d868..d97f813f5b9 100644
--- a/css-nav-1/Overview.bs
+++ b/css-nav-1/Overview.bs
@@ -391,7 +391,6 @@ the following requirements apply:
         as responses to pressing arrow keys would also be possibilities.
     </div>
 
-
 <div class=api>
 <h2 id="js-api">
 JavaScript API</h2>
@@ -1227,8 +1226,15 @@ run the following steps:
                 * bottom edge is above the top edge of <var>searchOrigin</var>'s <a>boundary box</a> if <var>dir</var> is {{SpatialNavigationDirection/up}}
                 * right edge is left of the left edge of <var>searchOrigin</var>'s <a>boundary box</a> if <var>dir</var> is {{SpatialNavigationDirection/left}}
                 * left edge is right of the right edge of <var>searchOrigin</var>'s <a>boundary box</a> if <var>dir</var> is {{SpatialNavigationDirection/right}}
-            * the item partially overlaps with <var>searchOrigin</var> and
-                its two edges which are orthogonal to <var>dir</var> should be on the navigation direction of the respective ones of <var>searchOrigin</var>.
+            * the item partially overlaps with <var>searchOrigin</var> and its <a>boundary box</a>'s
+                * top edge is below the top edge of <var>searchOrigin</var>'s <a>boundary box</a> if <var>dir</var> is {{SpatialNavigationDirection/down}}
+                * bottom edge is above the bottom edge of <var>searchOrigin</var>'s <a>boundary box</a> if <var>dir</var> is {{SpatialNavigationDirection/up}}
+                * right edge is left of the right edge of <var>searchOrigin</var>'s <a>boundary box</a> if <var>dir</var> is {{SpatialNavigationDirection/left}}
+                * left edge is right of the left edge of <var>searchOrigin</var>'s <a>boundary box</a> if <var>dir</var> is {{SpatialNavigationDirection/right}}
+                
+                NOTE: More detail condition about how the element is overlapped with the search origin affects the sequence of focus movement.
+                The sequence of focus movement is related to UX, so it depends on the UA-defined mechanism.
+
         2. For each <var ignore="">candidate</var> in <var>candidates</var>,
             [=find the shortest distance=] between <var>searchOrigin</var>.
         3. Return the item of the <var>candidates</var> set that has the smallest distance.