5:3 hundred and thirty years. It is possible that other children were born to Adam, particularly daughters, during this 130-year period, with only Seth being mentioned by name, in view of an implied revelation to Eve that he was the appointed son leading eventually to Christ.
5:3 begat a son. Adam was “created” in God’s likeness (Genesis 5:1), whereas Adam “begat” Seth in his own likeness. Jesus Christ is the only “begotten” Son of God (John 3:16).