Because hot air dried with a group that has a density that is less than the contraction, which will see a cut from the picture that there will be a gap, and the hole caused by the contraction of the tissue, and fiber.
The groups are baking hot air density, the less shrinkage. The clip can be seen that there are gaps and holes caused by the contraction of tissue fibers.
Since the group A with hot air density, the shrinkage, less. The clip can be seen to have the space and cavity caused by contraction of tissue and fiber.