@b based on previous experience, your NS inventory location and the Amazon FBA inventory numbers will never be in sync until after you do that inventory adjustment. If you're looking at near real-time inventory numbers for your FBA products, you will need to go the route of grabbing those numbers from Amazon reports via Amazon's MWS scheduled reports (mostly CSV plaintext formats) and then updating custom fields in NS to help you manage that inventory. Amazon has an internal process that moves the inventory across their warehouses and oftentimes they "misplace" items either during the receiving process or through moving the product across their warehouse systems.