Symptom
The dispatch-days field held 7, and we read that as "we promised 7 days." The live product page was showing 13.
Cause
The platform automatically adds 6 days of domestic handling to cross-border items. It's documented, but 13 appears nowhere in any response. A number absent from both request and response is the only number the customer ever sees.
★★★ That field is an input, not a final value. An item that actually takes two to three weeks, displayed as 13 days, is structurally late — and lateness erodes the seller score and ends in a selling suspension. It is not a per-item problem.
Fix
Target the displayed value and work backwards — target display − platform addition. Setting 14 produced the intended 20.
★★★ When a platform transforms a value for display, verification belongs on the output, not the input. Our 7 was correct and the customer's 13 was wrong — you cannot see that either is wrong without looking at both.
★★ This collection already holds two of the same shape — a catalog price that was in the store's display currency, and a cart quote that was too. Every point where "the value we sent" and "the value they display" diverge has to be checked separately. Getting burned once and fixing it does not make the next field safe.
How to verify
★ End the registration pipeline with "read the public page once and compare the key displayed values." Price, delivery days, option names — the customer's screen is the only answer key.