A new student approached the Zen master and asked how he should prepare himself for his training. “Think of me a bell,” the master explained. “Give me a soft tip, and you will get a tiny ping. Strike hard, and you’ll receive a loud, resounding peal.”
Here the Teacher wants to convey a message that its up to the student., how much he wants to get in return from him. The more he is eager to learn he will be able to get. This also proves that if there are 10 students of one teacher. The teacher will be ready to give his best to all but the output for every student depends on the effort of that every student.