On starting the app for the first time you'll be asked to provide monthly limits for calls, messaging and data, plus the day of the month on which counters should be rest. For many this latter setting will be the first of the month, but for others it will be the day they started their contract. The app will automatically reset the counter on the specified day every month.
Once the limits set it will start monitoring phone usage in the background. On the opening page of the app there's a tile for each usage type, with the background reflecting the usage / limit remaining.
Tapping on any one of the tiles (calls, messaging and data), takes you a pivot view for the appropriate type, which shows additional information. The first page of the pivot shows monthly usage (against the defined limit), the second shows total usage, and the third (voice and messaging only) shows a top contact list (sorted by number of outgoing / incoming minutes).
Counters app lets you manage your calls, messaging and data use each month. And there’s even the option to reset your counters on your monthly billing date.