php is a server side language - all calculations are done on the server. your timer is timing from when the server begins to execute the php script, to when it finishes executing.
data is sent to the browser (client) as soon as it is outputted by the script, but will only deliver as fast as the connection can handle (ie the script will finish long before the page finishes loading). This is quite a big page, and so takes a long time to deliver (although the script runs fairly fast). On mine it took about 6 seconds to load (i am on broadband).
if you want to show the display time of the page, you have to use a client side language (ie javascript)
adam
