256x256 is 4 times larger than 128x128, not 2 times

docs/documentation/elements/image.html

@@ -75,7 +75,7 @@ meta:
 {% include elements/anchor.html name="Retina images" %}
 
 <div class="content">
-  <p>Because the image is fixed in size, you can use an image that is <strong>twice as big</strong>. So for example, in a <code>128x128</code> container, you can use a <code>256x256</code> image, but resized to <strong>128x128</strong> pixels.</p>
+  <p>Because the image is fixed in size, you can use an image that is <strong>four times as big</strong>. So for example, in a <code>128x128</code> container, you can use a <code>256x256</code> image, but resized to <strong>128x128</strong> pixels.</p>
 </div>
 
 {% include elements/snippet.html content=retina_image %}