What do you mean' read slowly, read clearly'?

From Zhu Xi's Family Instructions

Auspicious slow reading, subdividing the meaning of clear reading

Read the words slowly and calmly. Read carefully and calmly.

Original paragraph

When reading a book, you must clean up several cases, put the books in order, stand up straight, read the books carefully and clearly. Don't miss a word, miss a word, miss a word, add a word, fall a word, and don't force your heart. As long as you recite more, it will be catchy and unforgettable. The ancients said, "Read it a thousand times and you will know its meaning." If you read well, you don't need to explain, you know what it means. I have learned three times, that is, heart, eyes and mouth. The heart is not here, the eyes don't look closely, the heart is not single-minded, it can only read, never remember, and it won't last long. Of the three, the heart is the most urgent. Since the heart is here, won't the eyes be there?

translate

But if you are reading, you should tidy up the desk for reading, make it clean and stable, put the book neatly upright, let your body sit up straight, face the book and read slowly and calmly. Read it carefully and calmly. Read every word loudly, don't mispronounce every word, don't read less, don't read more, don't turn the word upside down, don't know the article, and understand the content at will. Just read it a few times, and you will understand it naturally, and you will not forget it after a long time. The ancients said that if you read it several times, you will naturally understand its truth. So if you are familiar with this book, you can understand the general idea of the book without reading the explanation. I once said that I read three times, that is, my heart, my eyes and my mouth. If you don't pay attention, your eyes won't look carefully and your mind won't concentrate. You just pretend to read aloud with emotion, and you won't remember it deeply. Even if you can write it down temporarily, you won't remember it firmly. Heart to eye to mouth, the heart is the most important, read with your heart, and your eyes and mouth will not follow?