What is the meaning of chestnut old tree selection?

After picking chestnuts, they are bought from chestnut farmers, with different sizes and a small amount of impurities, commonly known as mixed purchase. Chestnuts used for roasted seeds and nuts need to be classified by screening equipment, and chestnut shells and impurities are screened out, and then stored in cold storage. In JD.COM, chestnuts are generally divided into the following grades according to the number of grains per catty: selected chestnuts (the largest, about 45 grains per catty), standard chestnuts (about 60-70 grains per catty, some of which are subdivided into large and small chestnuts), medium chestnuts (about 85 grains per catty) and small chestnuts (the smallest,1/kloc-0-0-). Of course, there is no official uniform standard for chestnut grades, and there may be differences among families.