We update the products twice a day automatically in our Marketplace to show the exact quantity. In the catalog settings, you can set what should happen with the out of stock products; you can either hide the products or set the quantity to 0 in your store.
1. In the Marketplace menu click on My catalogs
2. Click on your catalog
3. Click on Catalog settings
4. Choose if you would like to hide the product or set the quantity to 0