Genesis 5:12 Meaning

10And Enos lived after he begat Cainan eight hundred and fifteen years, and begat sons and daughters:

11And all the days of Enos were nine hundred and five years: and he died.

12And Cainan lived seventy years, and begat Mahalaleel:

13And Cainan lived after he begat Mahalaleel eight hundred and forty years, and begat sons and daughters:

14And all the days of Cainan were nine hundred and ten years: and he died.