[lots2learn]

This only describes one model of selling on Amazon i.e. as a vendor. The vast majority of sellers are not vendors and manage their own inventory quantities. The way the system qorks changed several times over the years, and was notably very constrained during COVID, but these days Amazon just provides a recommended qty per sku and an overall hard limit on total square footage each seller can use. The limit is determined by sales volume, so higher volume sellers get more space. If product doesn't move, the seller pays storage fees and eventually (more expensive) long term storage fees.