A scale will read a force value that is equal to the normal force exerted by the scale upon the object that is in contact with its top surface. By analyzing all the other forces that act upon that object, it is possible to predict a value for the scale reading.

 

The 5.0-kg box is at rest on top of the scale. It is being pushed downward by a hand. You want to know the scale reading - that is, the normal force acting between the box and the scale. To do so, consider the forces acting upon the box.

There are two contact forces - the normal force (upwards) and the finger pushing downwards. And then there is force of gravity (the Earth pulling the box downard). These three forces must balance each other since the box is at rest. So the one up force - the normal force - is equal to the two downward forces (one of them being the weight of the box). So from this type of analysis or reasoning, you should be able to determine the strength of the normal force relative to the weight of the box.