If you are refering to the Last terminal, it is probably that a Gene thing was put in the Humans so they would eventually rise to the same Tech level as the Forerunners, and the Librarian what's them to teach the Didact something, possible forgiveness, but I'm not sure if she was refering to the Promethean Knights when she said to help them, but she was probably refering to the Didact, seeing as she planned to give him the Janus Key to give to the Humans.