Task completion calculation

Hello, back with another question: how does GP calculate overall project completion from its tasks? Or task completion from its sub-tasks?
This figure appears in the pdf report and it would be good to know what it means. Thanks in advance and keep the excellent work you’re doing.

For each leaf task its completion is duration * percentage and this accounts for “completed days” of that task. If the duration of a leaf task is 10 days and percentage is 30% then its “completed days” virtual property is 3 days.

For each summary task the sum of all durations of child tasks is “planned days” and the sum of completed days of the child tasks is completed days of summary task. Completion percentage is completed days / planned days.

If you have a summary task with two child tasks, one with duration=10 days and completion percentage=50%, and another with duration=5 days and completion percentage=60% then planned days of the summary task is 15 and completed days is 100.5 + 50.6 = 5+3 = 8. And its completion percentage is 8/15 = 53%

The same calculations are applied recursively up to the project level.