How much did the two generations travel?

Afandi was tired of staying at home, so he decided to play outside. So the two generations got on the donkey and set off. The tourist destination of the two generations of love is the Great Wall.

Two generations fell asleep on the donkey's back when they rode halfway. When he woke up, he found that the distance left was only 1/4 of the distance he had traveled when he slept. He narrowed his eyes and knew that the donkey had walked a small part of the whole journey while he was sleeping.

Dear readers, do you know?

[Answer: 3/8. ]