Modify explanation of zero-indexed arrays

class2.html

@@ -147,7 +147,7 @@ <h3>Arrays -- returning values</h3>
             </code></pre>
           </div>
           <div class = "fragment">
-            Nerds are weird, so we start counting at 0.
+            Arrays in JavaScript are "zero-indexed", which means we start counting from zero.
             <pre><code contenteditable class = "javascript">
       var rainbowColors = ['Red', 'Orange', 'Yellow', 'Green', 'Blue', 'Indigo', 'Violet'];
       var firstColor = rainbowColors[0];