The paper is different and the weight is different.

If calculated by 150g copy paper, a book with 16 pages and 350 pages weighs about 1.64kg, which is more than 3 kg.

If the full opening is 150g based on 150g copy paper, then the opening of 16g is 150g/ 16g = 9.375g, that is to say, one page is 9.375g, and the book is printed on both sides, which is equal to.