get https://app.asana.com/api/1.0/projects//task_counts
Get an object that holds task count fields. All fields are excluded by default. You must opt in using opt_fields to get any information from this endpoint.
This endpoint has an additional rate limit and each field counts especially high against our cost limits.
Milestones are just tasks, so they are included in the num_tasks, num_incomplete_tasks, and num_completed_tasks counts.