When to use it. The shelf and the screen disagree: breakage, shrinkage, a picking error found, a delivery short-counted last month. The adjustment is the only correction path — there is no edit that quietly rewrites a balance, by design (1.6).
How it runs. Draft the adjustment (§5.7): name the product, the warehouse, and the quantity that should be on hand — the form works in targets, not deltas, so there is no arithmetic to get wrong. Say why, in the narrative: an adjustment without a reason is a number nobody can defend later, and the narrative travels with the movement forever. On posting, the difference between the recorded balance and your target is written as a movement, and its value — at the moving average — is posted to the adjustment account named on the document, so the books and the shelf come back into agreement in the same act.
For a lot-tracked product the correction names its scope: one lot, or the unattributed remainder (§5.6, lots and FEFO) — you correct the batch that is actually wrong, not the product in the abstract. And while a stock count covering a product and warehouse is open, adjustments to that pair are refused: the count owns the truth until it posts (§5.6, counting).