If a map is being reduced to form a pocket sized version then it is being proportionality reduced a smaller size that is required. Cartographers enlarge and reduce maps proportionally to serve different purposes in their study. The map is still the same but smaller in size.
If on a map 2cm represents 2 meters, that is 0.02/2 which evaluates to 1/100, then we are comparing distance and ensuring they are proportional using scale factor(our scale factor is 1:100 here)
