Damages
The plaintiff in a tort case must prove more than the fact that the defendant owed her a duty of care and that the defendant’s conduct breached that duty. The plaintiff also must prove that she suffered damages as a result of the tortious conduct, and must provide evidence of the amount of those damages. Without proof of damages, the judge or jury has no way to determine how much to award the plaintiff.
A reasonable estimate of damages may be made if there is some evidence to support it, but a court may not just "pick a number" that is unsupported by evidence.