All spreadsheet reports are broken down into several tabs including a Summary, Business List, Personal List, and Pending List. The Business List tab is all of the trips/transactions that you've tagged as business, while the Personal List tab is all of the trips/transactions that you've tagged as personal. The Pending List tab lists all of your untagged data, so if there are any trips/transactions that you have not yet tagged, they will be listed in the Pending List tab.
To categorize the trips/transactions listed in the Pending List tab of your report, you will need to tag them as Business or Personal in the app. Once tagged, you can export an updated report to see your changes reflected.