Journal
A value without its source is a claim. A value with its source is a fact anyone can check.
The question every reviewer asks
When a number looks wrong, the first thing a reviewer wants is the page it came from. Without a mark, that means finding the file, opening it and searching. With a mark, it means one click.
What a mark records
Each mark stores the input, the page or line, and the position of the value on it. For a recording, it stores the time. The mark is kept when a value is corrected, so the record shows both what the input said and what a person decided.
Where marks travel
Marks are shown in the review queue and the history, and they are included in every export as a column or a JSON field. Teams that send results to a data warehouse often keep the mark column, because it answers audit questions later.