The simplest way is for the AI to show where it found every value, ideally by linking to or highlighting the exact location in the source document. A reviewer can then check any value in seconds rather than having to trust the output or search the document themselves.
If a value cannot be traced to a source, it should be marked clearly as uncertain or missing rather than filled in. That one rule, no value without a source, is the most useful protection against AI inventing information in industrial documents where accuracy matters.