Units indicate the percentage of time a resource will spend working on a task. For example, if you assign a person to work full-time on a task, you’d assign that person at 100 percent units. If you want that person to spend only a quarter of his or her available time on the task, you’d assign that person at 25 percent units. When you assign a set of resources to a task, 100 percent units means you’ve assigned one resource from that set to work on the task full-time, 200 percent means you’ve assigned two resources from the set, and so on.