How many years before Abraham was the flood?
The flood is placed about 400 years before Abraham in the round-figure chronology. Abraham is dated near 2000 BC, so the flood falls roughly four centuries earlier, according to the timeline presented. These are approximate, memorable round numbers rather than exact years.
Les explains that the chronology is set in round terms for memory, starting from 4004 BC for Adam's creation. He places Abraham at 2000 BC, halfway between Adam and Christ's first advent. Then he says that backing away from Abraham about 400 years in round figures brings us to the time of the flood. So the flood is roughly 400 years before Abraham.