A scale copy is basically to copy the same geometrically figure but at different sizes of the original figure. The copy will be bigger or smaller than the original one. It will depend on the factor to scale the figure.
For example, if we want to duplicate the size of the original figure, we need to multiply by 2 each size of the figure. In this case, the figure is bigger than the original one by a factor of 2.
Conversely, if we need to have a smaller representation of the original one, we can multiply each side of the original figure by a fraction. It could be 1/2, 1/10, 1/75, and even 1/100, and so forth. The factor will depend on the needs about how to represent the original figure on an appropriate scale. In this way, if we have a size of b, we need to multiply it by the factor above mentioned, for instance:
Scale copy is fundamental in Design, and whenever is necessary to represent the original object on a different scale.