Hi Sara4,
The Purchase > Bills window is filtered by date ranges, while the Unpaid Bills report shows information up to a certain date, including all transactions from the start of the file. I suggest changing the start date in the Purchase > Bills window to include all transactions from the conversion date. This way, the filters will match the dates for the Unpaid Bills report.
If the values still don't match the report consistently, creating a support ticket from the My Account page might be best for further troubleshooting.
Thanks,
Genreve