In KaHero POS, you can sell an item by weight and this is determined when you first create an item and chose the "Sold By Weight" option.
Firstly, set your item to be sold by weight. You can edit this on "Items" under the "Listings" tab on the Navigation menu.
On the "Register" screen, select the item and a pop up will appear for you to input the desired quantity.
On the tickets at the right side of the register, the item should appear with the desired quantity multiplied by the price by weight of the item.