Summary:
In a report, the billable and non-billable hours are seen on the same row of a time entry date or different rows is based on how comments are entered along with the daily hours.
If no comments or exactly same comments are entered for both billable and non-billable hours then the report shows the time entry as billable and non-billable hours in a single row.
If comments are entered for either billable or non-billable, or If comments for billable and non-billable hours are different, then the report shows that days time entry in two separate rows.