It means that when reading, not thinking or taking notes is worse than not reading.
What is low-key here is the method of reading. There are three ways to read, namely, the heart, the eyes, and the mouth. If the mind is not on the book, then the eyes will not read carefully. Since the mind and eyes are not concentrating, but just read casually, they will definitely not be able to remember it, and even if they can remember it, they will not last long. Among the three, the heart is the most important. Now that the heart has arrived, the eyes and mouth will also arrive.
There are three aspects of reading, namely, understanding with the heart, understanding with the eyes, and understanding with the mouth.
Zhu Xi was a master of Neo-Confucianism in the Southern Song Dynasty and a famous educator. He spent most of his life reading and teaching and provided many insightful insights. Shortly after his death, his disciples summarized his reading experience into six items, which he called "Zhu Xi's Reading Method", which still serves as inspiration and reference for today's people.