To set up two-step verification:
  In Seller Central, go to Settings > Login Settings.
  Sign in using your user login and password.
  For Advanced Security Settings, click Edit, and then click Get Started.
  Choose your preferred method of receiving the code:


Via text message (SMS)/voice call by entering your full phone number. 
Via an Authenticator app (e.g. Google Authenticator, Microsoft Authenticator, downloaded from your phone’s App store) by scanning the QR code.

 Enter the code that has been generated, and then click Verify code and continue.
 Select your backup method, for when you do not have access to your preferred authentication method. This can be done via text message (SMS) /voice call to another mobile phone number or via the Authenticator app.
Enter the code that has been generated using the backup method, and then click Verify code and continue.
  因为账号比较多，之前认为后台不会强制，现在6月30之前必须完成，如果全部采用手机很麻烦，要很多号码。
所有两步验证第二步骤都采用 Authenticator app，所有账号都用一个Authenticator app 扫描来生成QR code 账号又没关联的可能性啊； 
 哪位大神用过，或者各位大咖用过，分享一下；