I think the AppleCare statistic was of the total amount of iPhone users. (5-10million?)The key point here is that 0.55% is a percent based on the of iPhone 4 users, not the number of calls to Apple Care.
For example, supposing only 1% of iPhone 4 users called Apple Care, then half the calls were about the antenna issue. Now consider that Apple Care handles technical issues with every product Apple produces, not just the iPhone.
edit: nevermind