Here's what KMOV reported:
About 500 people in February 2009 held a tea party protest on the riverfront. The party wants to show that the movement is a political force with staying power. Today, that number was up to 10,000.The implication is that the tea party grew from 500 to 10,000 people. Even if the 10,000 number was correct (which I don't think it was), the rally earlier today was one of three national tea party events being organized by a national group Tea Party Patriots, while the previous rally was only for St. Louis. They're comparing apples and oranges.
All of the other news stations seemed to notice that fact.