is normal speed
is half speed
(using a number greater than 1 will result in the progress going outside the boundaries of the progress bar (I think the numbers control just the white/gray area and not the boundary extents of the bar))
(EDIT: As petr said, it's values between 0 and 1, so that makes sense why it goes past.. if you're pressed for time or just don't care, you can keep the larger number and just hide/mask the part that goes outside the boundary.)
is even slower
Basically you can play with multiplying or dividing to alter the speed.
Just so you know, you can add /inspect to the end of a watchfaces' url to inspect it and see the code behind the watch if the designer enabled it. In the above example, just click on "Test Rator" and it'll open the watch in a new window. If you see a little rocketship on the left side, you can click it or add /inspect to check it out.