There are three dialogs in the Usage Meter section. To move between them swipe your finger from left to right (or right to left).
To set the cellular data limit:
This dialog will display a list of the user’s top ten applications in order of their data usage (showing the total usage and each applications percentage of the total).
This dialog will display your twenty most recent network connections. Tap trashcan button, if shown, to clear the connection history.