Uploadify Progress Bar

Can someone please tell me if the progress bar in the Uploadify plug-in will jump from say 0% to 10% to 17% etc. automatically, or does it need special code?

I'm working on a project to use the Uploadify flash plug-in to upload images to a site. I'm trying to see if the Progress Bar is working correctly, but can't get anything other than it jumping from 0 to 100%. I'm testing locally and have tried using the Firefox Throttler plug-in and a very large image file, but both don't seem to make a difference.

When I upload the same image to the demo on uploadify.com, you get the correct 3%, 10%, 17% etc. I had a look at the code here and I don't see anything special that updates the progress bar, so am wondering if it'll just work nicely when I put it 开发者_运维百科live.

Thanks