Smartphone values are based on testing with the Android operating system. Usage with other operating systems may vary. These are just estimates, and data transfer amounts will vary based on application. Downloads that buffer, such as streaming music and video, will bill for all of the data that has been downloaded, even though you may not have listened or watched the entire download. Please regularly check and manage your usage. Use of Gmail, Exchange, and other email servers may increase data utilization due to syncing of PIM data such as calendars, contacts, etc.