Thats it. When you are buying from a store, you cant se how many of the item someone has. But If you want to sell, unless you reach the max ammount of mats that the person want to buy. You cant know exactly how much to sell. May be someone of your clan see someone buying some material in another city at a very good price, it can results in you walking a lot (or using the gk), just to see that you only sold 10 units of the material instead of 1500 you had. Or you just have the mats on the warehouse, and you dont want to just try to guess how many is someone going to buy. I dunno. I think it can be a good feature to add.