1, the discount means "multiple copies are sold together". For example, five packs of 12 are discounted, and one pack of 2.5 is called retail or single sale. Calculated, the discount unit price is cheaper than a single package, which is considered as a "medium package" discount.

2. Sales by volume means sales by volume. Actually, it's a word from China and Taiwan Province province. It refers to the supermarket packaging vegetables and other items by itself, and then labeling them by weight. In Chinese mainland, it has become synonymous with some supermarkets.