Add some documentation

svelte/src/speedtest/Index.svelte

@@ -20,10 +20,12 @@ import Speedtest from "./Speedtest.svelte";
 		</p>
 		<p>
 			The speed measured is the maximum speed reached for two continuous
-			seconds during the test. The normal test has a time limit of 30
-			seconds and the long test 60 seconds. When the maximum speed has not
-			changed for a third of the test duration (10 or 20 seconds) the test
-			will end and the result will be final.
+			seconds during the test. The normal test has a time limit of 15
+			seconds and the long test 30 seconds. When the maximum speed has not
+			changed for a third of the test duration (5 or 10 seconds) the test
+			will end and the result will be final. The long test will use much
+			more bandwidth, so if you're on a cap it's recommended to use the
+			normal test.
 		</p>
 		<p>
 			The speed gauge uses a logarithmic scale, which means that each