By setting realistic targets then the work doesn't look too overbearing and appears more easily manageable.
By breaking the work load down like this then the pupils will feel less intimidated by the work expected of them and should hopefully feel more inclined to complete it to gain that all important praise as their reward. Feedback is a good motivator. It encourages them to look at their work and see where it needs improving. This can help them gain satisfaction from their learning and teach them to start to look at their work