docs: clearification

Author: mfranzke

demo/index.html

@@ -91,7 +91,7 @@ <h1>
 			</blockquote>
 
 			<p class="scrolling-advice">
-				Please scroll down to the very end of this demo page to see these images being loaded by the polyfill on
+				The following whitespace is included as a threshold, <strong>please scroll down to the very end of this demo page</strong> to see these images being loaded by the polyfill on
 				<a href="https://caniuse.com/loading-lazy-attr">unsupported browsers</a>
 				<span aria-hidden="true">⬇</span>
 			</p>