Moses couldn't remember from one verse to the next How long was the ark afloat?
For seven months or so.
Genesis 8:4
And the ark rested in the seventh month, on the seventeenth day of the month, upon the mountains of Ararat.
For at least ten months.
Genesis 8:5
And the waters decreased continually until the tenth month: in the tenth month, on the first day of the month, were the tops of the mountains seen