Question about step 10 and 15

[bindvori]

hello, i got a question,

8. Double-click on Internet Protocol Version 4 (TCP/IPv4)
9. Click on Use the following IP address
10. Enter a false IP like 123.123.123.12311. Press Tab and the Subnet Mask section will populate with default numbers
12. Hit OK twice
13. Right click the active Local Area Connection again and choose Properties
14. Double-click on Internet Protocol Version 4 (TCP/IPv4)
15. Choose Obtain an IP address automatically


here we are enter manual an ip (point 10) and we changing to settings as Choose Obtain an IP address automatically again (point 10). if we back to first setting that connect with automatic ip, why we are enter manualy ip ?

note: i am using robotics cable modem.

thank you