We advise against manually editing product quantities directly on the marketplace, because these changes will be overwritten the next time your inventory feed is updated from Omnivore.
Instead, if you need to adjust a product's marketplace quantity without altering the quantity in your eCommerce store, use the Promotions feature in Omnivore.
This approach keeps your feed data consistent and avoids conflicts.
More information about promotions is available under the Pricing and Promotions section.
Specifically when creating a new Promotion you can use this option here on the Add New Promotion page.
