The answer is Yes. The task Duration field is a hidden field that is calculated in the back end of PPO.
Background:
In Microsoft Project, the task duration is calculated when creating your project schedules. When those schedules are imported into PPO the task duration is also imported and reflected in PPO (as per the screenshots below).
If you are not using MSP and are either manually adding tasks in PPO or using the Excel template, the task duration is automatically calculated in the back end.
Why is Duration important?
On a project level, PPO calculates the overall Actual % & Planned %. These calculations take into account the duration of all tasks in your schedule where the Type is Task (it excludes the project task, summary tasks & milestones). If a task did not have a duration, the Planned & Actual % on Project level would not calculate, therefore we have made provision for duration to calculate automatically.
The Actual & Planned % fields on the Project entity are used widely across all reports and dashboards in PPO.