This was written in the Shopper Messages last year:
"Please note that we cannot alter or amend or swap out data in a report after it has been submitted and processed. It is up to each Shopper to carefully review the shop guidelines and provide all the data that is requested prior to submitting the report. After that, it is too late to alter your report. "
That said, I do know shoppers who realized they submitted a report with an error, e-mailed explaining, and the editors did work with them. It seems to all boil down to who happens to check your report.