If you have more than one registered mobile device, each with more than one phone number or email address registered, a prompt appears for you to select which mobile device, phone number, or email address to use in the second-factor authentication workflow.
1. Select the Second Factor authentication option – for example, "4".
2. Click Continue.
3. Since option 4 was selected in this example, a prompt appears for you to select the phone number where the passcode will be sent.