Solved
TurboTax shows an error: "The document number's first 3 characters must be entered". There is nothing before the 10 characters I entered, other than "Doc#"
The problem was that I put in all 10 digits instead of the first 3. I don't know why this text field accepts more than 3 digits.
I didn't read carefully enough (the wording of the hep text is confusing though), my bad.
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