inventory control

Hi,

Well, that's the way it works so there is nothing to correct. It's the normal behavior.
There are several ways you can have inventory control on your products with variants:
- You configure the quantity only in the main product and leave the quantity unlimited in the variants. In that case, the quantity will be updated for any variants purchased. The quantity of the main product will be the quantity of all the variants of the product.
- You configure the quantity only in the variants and leave the quantity unlimited in the main product. In that case, each variant's quantity will be independent from one another and only the quantity of the variant purchased will be updated.
- You configure the quantity of each variant in each variant, and the total quantity of all the variants in the main product. In that case, both the quantity of the variant purchased and the quantity of the main product will be updated when you purchase a variant.

In your case, since you configured a quantity in both the main product and the variants, you're in the third case and so it's normal that the product quantity and the variant quantity is updated.