Adjust

Adjusts the inventory count for a product at a location. It is different from Inventory Refresh because rather than stating the total quantity of the product, this adjustment specifies the amount of change in the form of increments and decrements (+/-). Increments do not require a + sign and may be sent as a simple integer, but decrements must include the – sign. For example, there would be a -2 quantity for an item if there were two fewer than in the previous count, a 2 quantity if there were two more, and a 0 quantity if there were no change.
These requests are placed into a queue of jobs that are processed one at a time. Due to this, the best practice is to submit fewer requests with more items per call, rather than numerous requests with a small number of items each. However, unlike the Refresh API that accepts a maximum of 12000 items per call, this Adjust API only accepts up to 1000 items. If you exceed that limit, a Bad Request error will be returned.