Is this switch ok for a 15A circuit?

Hi all -

I am considering a timer switch for a bathroom ceiling fan, which is on a 15A circuit. The switch is advertised as 20A. Is it safe/correct to assume that this would work on a 15A circuit as well?

Here is the switch:

http://www.smarthome.com/4253w-b.html

Reading the available online manual, it shows connection details for a 20A circuit, and what I assume is mislabelled as a 5A circuit.

I think it should be fine for my 15A circuit, but I thought I'd ask the experts here

You can use a switch rated for higher than the load. Used at a lower wattage, they may last longer because of the heavier duty contacts.

OK, thnx, makes sense too.