When you sign up for a Pro Twitter Stats account we start recording your Twitter data. Twitter Counter cannot display statistics for data that was not recorded. Since you've just subscribed to our Pro Stats service, the first 30 minutes you will only see the CSV files from the last 30 days. So next month you'll have a complete and very accurate CSV file with all your stats from the past month.
Regarding historical followers growth stats, have you seen: http://twittercounter.com/pages/buy-stats yet? Here you can purchase the statistics for a one-time fee of $29 and get everything we know in a neat and tidy CSV file.