In a recent data review, we discovered a bug that was either under-reporting or over-reporting the total number of users who had authorized some Platform applications. We're correcting this number today, so you might see a different number of total users reported on your application's Insights page. This won't change the number of monthly active users reported for any application, which is the primary user count we publicize.
We've long believed that the true reflection of your application's success is best gauged by user engagement, which is why the monthly active user count is the metric we publicly display in search results and in the Application Directory. There were no reporting errors for monthly and daily active user totals (MAUs and DAUs, respectively). Both active user totals are determined daily; MAUs include users active within the 30 days prior to today, and DAUs include users active within the past 24 hours. Thus you always have the most current and accurate totals for user engagement with your application.
The total user count was an informational number you could use to track how many users have authorized your application. This number only appears on your Insights page, and is not public facing.
The Insights page contains a wealth of information and statistics about your application. You should check your Insights page often. Go to http://www.facebook.com/business/insights/app.php?id=YOUR_APP_ID
We always welcome your feedback. Please share it on the Developer Forum.