Integrating products in zoho commerce with items in zoho books

I am creating a site to sell fruits and vegetables on zoho commerce. We already are using Zoho books to do our accounting and billing in our store.

For example, we buy and sell carrots. Carrot is an item on zoho books, which is measured and tracked in kgs. We purchased, say 50kgs of carrots and entered the purchase on our books.

When we sell 500g of carrots to a customer, we enter it as 0.5kg on our bill on Zoho books and we are able to track the item inventory too.

Now, we are working to add Carrots on our zoho commerce site (with customer purchase options of 0.5kg and 1kg). These are not attributes of the product. How do we enable the dropdown on the commerce site? How do we integrate this with Zoho books?? (please see example from another site)

Thanks.
Narayan