Arcana Coelestia #486
486. Verse 4 And the days of Man after he beget Seth were eight hundred years; and he beget sons and daughters.
'Days' means periods of time and states in general. 'Years' means periods of time and states in particular. 'Sons and daughters' means the truths and goods that they perceived.
Genesis 5:3
3
Adam lived one hundred thirty years, and became the father of a son in his own likeness, after his image, and named him Seth.