Hi J.R. Ignacio, I saw you highlight this line. I think you got confused with this:
Enter file in which to save the key (/home/demo/.ssh/id_rsa):
/home/demo/.ssh/id_rsa is just the default directory displayed to you when you enter
ssh-keygen -t rsa. You can change the directory to
id_rsa_gitlab or any name you like.
Let me know if you need help.