The SKU of the consumable material differs from the SKU of the equipment. For Equipment, an SKU is a unique identification number of a specific material object. For example, you have a position "JBL SRX712 speaker system" in the amount of 12 pieces. So, in the Catalog GOLOVA you need to create 12 SKUs for this position. So, you will be able to track the movement and history of each individual object. 

For Consumables, this approach is excessive — you are unlikely to track the movement of each AA battery or work gloves or screws, etc. piece by piece. Therefore, you can create one SKU with a variable quantity for Consumables.

Example. 

You have two 200L barrels of glycerin in your warehouse. An SKU with a barcode is pasted on each barrel. Before the project, you pour 5L from one barrel into a canister. Here's how it will look in the Catalog. An item of the "consumable" type, which is called "Glycerin" with a unit of measurement in liters (l.). Two SKUs have been created inside this item, one for each barrel. In the card of the SKU, the quantity is set to 200. When shipping to the project, specify the number of 5. Upon completion of the project, the total number inside the SKU in the catalog will change and become 195, because it is assumed that you have used up consumables on the project.

By default, the system will create an SKU of consumables in the amount of one, in order to avoid errors and confusion. Once again: the SKU of the consumable is a common number for a group of objects. And the number of objects is set in the consumables card.