Understanding hours reporting
A time entry or a presence can be linked to a task if the task was worked on during that time and if you want to report it. Each time entry can be only linked to one task.
Simple reporting is done by linking one task to the time entry.
Advanced reporting is done by subdividing the total hours included in the time entry between more tasks. In this case the time entry will be divided into more time entries for each reported task. If there are still hours not being reported a new non reported time entry will be created. Advanced reporting is possible only for non reported time entries.