In Genesis 7:6, this refers to Noah's initial state of temptation. This is clear from the fact that from here on to Eber in Chapter 11, the numbers, years of age, or names all refer to real things, as was also the case with the ages and names of all those mentioned in Chapter 5. Here 'six hundred years' means the initial state of temptation. This becomes clear from its prime factors, which are ten and six multiplied again by ten.

(References: Arcana Coelestia 737)