They're obviously using the 537 day as for when the jews returned and then adding 70 years to get 607
The idea that the 70 years finishes in 537 can be shot down using one scripture in the Bible. Jer 25:12:
12 “‘But when 70 years have been fulfilled, I will call to account* the king of Babylon and that nation for their error,’ declares Jehovah, ‘and I will make the land of the Chal·de′ans a desolate wasteland for all time.
On JW. Org when you click on the * it says punish.
So the question for your parents is, when does this 70 years end? Presumably they will say 537. But then ask them how can you punish a King who hasn't been in place as a king for two years? He was overthrown in 539!
Even the Bible contradicts WT theology. I guess the Bible is wrong huh?