This generally occurs because a Discount Code was used when the registration was purchased.
You can correct this negative value for the current registration in the batch via the following steps:
- Click on the gift displaying a negative value
- Click on the "Gift" menu and go to Links > Event > Registration Fees
- Change the entry in the "Amount Applied" section to equal the "Gift amount" and click OK
- Change the Receipt Amount to $0
- Save these changes or Commit the batch