The formula is a metric of the average retail rate of the providing company. It's a function of the revenues that the provider gets from the services. The three services that are covered by this section are: wireless voice, wireless data, and wireless text services.
For a company that is providing the wireless roaming service to another company, the formula looks at what the total revenues are that the company gets, for example, from its wireless voice services, and it provides a specific definition on that divided by the number of minutes it provides. It's a metric of the average rate; the average revenue per minute, or per megabyte in the case of data, or per text in the case of text the carrier generates in revenue from that particular service.