‘And after the flood Noah lived 350 years. All the days of Noah were 950 years, and he died.'
This directly connects back with Genesis 5 showing the unity of the whole section. The separate covenants have been deftly combined into one whole. It is possible that ‘three hundred years and fifty years' was intended to depict a full life (three is the number of completeness) and a life of faithfulness to the covenant (five is the number of covenant). To the early readers and hearers numbers were full of significance.