Thanks for reaching out. Here at Twitter Counter we track over 67 million Twitter accounts, as you can imagine this requires a lot of resources. To keep everything to a minimum we only track a 'normal' account every now and then, if we miss a couple of days of data we try to calculate it as accurate as possible. Premium accounts will get tracked every hour, so they are a lot more accurate. Besides that we're use caching, this means that you may see data that is up to 24 hours old.
If you want to have more accurate and daily updated stats, you can also subscribe to a weekly Twitter Stats newsletter update. This way we update the stats daily and keep you weekly updated about your progress. Just fill in your email address over at twittercounter.com/pages/settings.