Canon DR-7580 Instructions Manual page 82

Chapter 6 Troubleshooting
Error code U02
Cause Number of scanned document sheets is less than the set
number of sheets in the verify scan.
Remedy Two or more sheets may have been fed when the document is
scanned. Press the [Stop] key to reset the counter to "0." Check the
number of scanned images with the number of document sheets to
see if all document sheets have been correctly scanned, and scan
the document again.
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