[css-round-display] Clarify the definition of angle value for offset-path

Author: Jihye Hong

css-round-display/Overview.bs

@@ -415,7 +415,7 @@ Values have the following meanings:
 <dl dfn-for="offset-path">
   <dt><<angle>></dt>
   <dd>
-    The path is a straight line that has the degree of the angle as specified in <<angle>> from the Y-axis. The initial position of the path is the center of the containing block and the end point of the path is on the edge of the containing block.
+    The path is a straight line that pass through the center of the containing block and has the degree of the angle as specified in <<angle>> from the Y-axis. The initial position of the path is the center of the containing block and the path ends at the edge of the containing block.
 
     <p class="note">Note: Defining the path with <<angle>>, the element can be positioned in the polar coordinate system. In polar coordinates, a pole is the reference point and points are described as been a certain distance from it, as also a certain angle from the polar axis. In mathematical theory, the polar axis is commonly defined as the positive direction of the x-axis, but we consider the polar axis as the positive direction of the y-axis position as other CSS specifications usually do. Therefore, when the <<angle>> value of 'offset-path' is 0, the element is positioned on the y-axis. If the <<angle>> value increases in the positive direction from 0, the element moves clockwise. The method to determine a direction using the <<angle>> value for 'offset-path' works the same way in [[!CSS3VAL]], <<angle>> value.</p>
   </dd>