What does it mean to be notified by the official mobile phone number when changing the Apple ID password?

The reset operation is:

Step 1: Log in to Apple official website, click "Technical Support" and select "Reset Password".

Step 2: Enter the email address of the AppleID account on the AppleID reset page, and click the "Next" button.

Step 3: There are two ways to get it back. Don't take it back to email or answer security questions.

Step 4: Select one of the methods, and reset the account password after the personal information is verified.