[css-round-display] Modifiy the definition of the bounding box for the viewport

Author: Jihye Hong

css-round-display/Overview.bs

@@ -166,7 +166,7 @@ The current 'device-radius' media feature was derived from the syntax of 'border
 <h2 id="extending-viewport-rule">Extending the @viewport rule</h2>
 <h3 id="viewport-fit-descriptor">The 'viewport-fit' descriptor</h3>
 <p>
-'viewport-fit' can set the size of the bounding box which is used to apply the initial viewport.
+'viewport-fit' can set the size of the bounding box for the viewport which is the viewing area used to apply the initial viewport. And we can see the actual viewport through the bounding box.
 </p>
 <pre class=descdef>
 	Name: viewport-fit

css-round-display/Overview.html

@@ -443,7 +443,7 @@ <h3 class="heading settled" data-level="3.1" id="device-radius-media-feature"><s
     <p class="issue" id="issue-58ee1dc5"><a class="self-link" href="#issue-58ee1dc5"></a> The current <a class="property" data-link-type="propdesc" href="#descdef-media-device-radius" id="ref-for-descdef-media-device-radius-13">device-radius</a> media feature was derived from the syntax of <a class="property" data-link-type="propdesc" href="https://drafts.csswg.org/css-backgrounds-3/#border-radius">border-radius</a> to specify various shapes, but its usage is a little complicated with several issues. For simplicity and obviousness, <a class="property" data-link-type="propdesc" href="#descdef-media-device-radius" id="ref-for-descdef-media-device-radius-14">device-radius</a> would be changed with the revised syntax. (e.g. Am I round or rounded corners?) </p>
     <h2 class="heading settled" data-level="4" id="extending-viewport-rule"><span class="secno">4. </span><span class="content">Extending the @viewport rule</span><a class="self-link" href="#extending-viewport-rule"></a></h2>
     <h3 class="heading settled" data-level="4.1" id="viewport-fit-descriptor"><span class="secno">4.1. </span><span class="content">The <a class="property" data-link-type="propdesc" href="#descdef-viewport-viewport-fit" id="ref-for-descdef-viewport-viewport-fit-1">viewport-fit</a> descriptor</span><a class="self-link" href="#viewport-fit-descriptor"></a></h3>
-    <p> <a class="property" data-link-type="propdesc" href="#descdef-viewport-viewport-fit" id="ref-for-descdef-viewport-viewport-fit-2">viewport-fit</a> can set the size of the bounding box which is used to apply the initial viewport. </p>
+    <p> <a class="property" data-link-type="propdesc" href="#descdef-viewport-viewport-fit" id="ref-for-descdef-viewport-viewport-fit-2">viewport-fit</a> can set the size of the bounding box for the viewport which is the viewing area used to apply the initial viewport. And we can see the actual viewport through the bounding box. </p>
     <table class="def descdef">
      <tbody>
       <tr>