Update getusermedia.html

getusermedia.html

@@ -5136,7 +5136,7 @@ <h1>Privacy Indicator Requirements</h1>
       indicate when the value changes.</li>
       <li>Any false-to-true transition indicated MUST remain observable for a
       sufficient time that a reasonably-observant user could become aware of
-      it (this SHOULD be 3 seconds).</li>
+      it. This SHOULD be at least 3 seconds.</li>
       <li>Any of the above transition indications MAY be combined as long as
       the combined indication cannot transition to false if any of its
       component indications are still true.</li>