When reporting on the [incident_task] table, the user may want to show the Parent Incident related to the Task record. When the column Parent.Number is used, the user will see (empty) in the field.

The report will need to retrieve the data from the Incident Number field and not the Parent Number field.

Add the column Incident.Number and remove the column Parent.Number on table [incident_task] and use the column Incident.Number for your report.