Thanks for reaching out! From the moment you subscribe, as a Premium user, we will start saving and storing all "available" Premium Stats (retweets & mentions) from your account from Twitter on the export stats page. Since you've just subscribed to our service yesterday, you will only see the CSV files from the last 30 days. Next month you'll get a complete CSV file with all your premium and basis day to day followers stats from the past month.
With that said, we do try to get as much Pro Stats for your account from Twitter. Unfortunately, Twitter also has to deal with system availability. Which means in some cases we can't retrieve historical Premium Stats at all (but most of the times at least a couple of days).
If you require further information about your Premium account please email firstname.lastname@example.org.