The Remaining Actual Tasks field shows the total number of actual subtasks that remain to be completed for a summary task on a given day. If the project summary task is displayed, the Remaining Actual Tasks field shows the total number of actual tasks and subtasks that remain to be completed on a given day for the entire project.
Data Type Number
Entry Type Calculated
How Calculated When you first create a summary task, the Remaining Actual Tasks field for the task is equal to the total number of subtasks. When you mark one of its subtasks as 100% complete in the % Complete or % Work Complete fields, Project subtracts that subtask from the total number of subtasks for the summary task, and displays the result in the Remaining Actual Tasks field.
Alternatively, when you change the Actual Work field to a number equal to the subtask’s Work field, the same thing happens: Project subtracts that subtask from the total number of subtasks under the summary task, and displays the result in the Remaining Actual Tasks field.
When you first show the project summary task, the Remaining Actual Tasks field is equal to the total number of tasks and subtasks in the entire project. When you mark one of the tasks or subtasks as 100% complete in the % Complete or % Work Complete fields, Project subtracts that from the total number of tasks and subtasks for the entire project, and displays the result in the Remaining Actual Tasks field.
Alternatively, when you change the Actual Work field to a number equal to a task or subtask’s Work field, Project subtracts that from the total number of tasks and subtasks in the entire project, and displays the result in the Remaining Actual Tasks field. Note: Project includes subtasks and regular tasks in this calculation, but it does not include actual summary tasks (a task that includes subtasks).
Best Uses Create summary tasks that contain one or more subtasks. Add the Remaining Actual Tasks field to the timephased portion of the Task Usage view when you want to display how many actual subtasks remain to be completed on a given day for a summary task.
Example The "Write proposal" summary task has 3 subtasks: “Write”, “Edit,” and “Revise.” The “Write” subtask is scheduled to be done on day 1. The “Edit” subtask is scheduled to be done on day 2. “Revise” is scheduled to be done on day 3.
You mark the “Write” subtask as 100% complete. Therefore, the summary task’s Remaining Actual Tasks field for day 1 is 2. The two other subtasks are not yet 100% complete. Therefore, the Remaining Actual Tasks field for the summary task remains at 2 for days 2 and 3.
Remarks

The Remaining Actual Tasks field will not subtract a subtask or task unless you enter exactly 100% for either the % Complete or % Work Complete fields. Nor will it subtract a subtask or task if you enter a value of actual work that is less than the Work field.

Subtasks will always display a 1 in the Remaining Actual Tasks field until they are complete, or until they have been assigned actual work that is equal to the Work field.

You can turn on the project summary task on the Advanced tab of the Project Options dialog box.