URL refresh in passive mode

When I use one of my gateways in passive mode, the popup displays the 
following:
1) Initial popup has a URL refresh to the auth server with a waiting 
time of 450 seconds (my gateway has a loginTimeout of 600 seconds).
2) After the first refresh, the popup source shows a URL refresh as

  <meta http-equiv="Refresh" content="5; URL=http://192.168.89.1:5280/?ticket=<really-long-ticket-string>

3)The setTimeout javascript function still exists, where it resubmits 
the RenewalForm every 450 seconds.

My questions:
1) Is the popup being refreshed from the gateway every 5 seconds? I 
don't seem to find that traffic in ethereal.
2) Why 5 seconds? Why not 450 seconds?
3) If the page reloads every 5 seconds, why have the setTimeout function?

Any insight would be great.
--
Sameer