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.
Daniel 4:3
3
How great are his signs! and how mighty are his wonders! his kingdom is an everlasting kingdom, and his dominion is from generation to generation.