How does Apple's mobile phone blacklist strange numbers?

Taking Apple 6sp as an example, the specific operation method of blacklisting strange numbers by Apple mobile phone is as follows:

Steps:

Step 1: Open "Phone" on Apple's mobile phone, enter "Recent Calls", find the phone number to be blacked out, and click "I" at the back.

Step 2: Then click "Block this calling number"

Step 3: Finally, select "Block Contacts" to blacklist this strange number.