homework and exercises - How quickly was the Earth rotating 250 million years ago?

The Earth is slowing at a rate of $4.7\times10^{-4}$ miles per second every 100 years due to tidal forces of the moon.

See:

250 million years ago, it would have been spinning at 4.2 million miles per hour! The dinosaurs would have flown off the earth.

If the deceleration rate is inaccurate by 95% (assume it is slowing more slowly), then 250 million years ago, it would be spinning at 213,000 miles per hour.

Also, given the fact that the moon is receding from the Earth, the effect the moon has on the Earth would have been greater in the past.

I don't understand; can someone explain?