They're moving from reporting subscription revenue on a monthly basis to a daily basis. They were counting the first month of an annual subscription as a full month of income. Now they'll only count from the day the subscription is sold.
It doesn't sound like a big deal, but who knows what goes through the mind of some investors.
[link|http://www.redhat.com/about/presscenter/2004/press_restatement.html|http://www.redhat.co..._restatement.html]