Scale factor could result to enlargement or reduction. A scale factor greater than 1 results in enlargement while a scale factor lesser than 1 results in reduction.
Looking at the given figure, each small box represents 1 unit.
For example,
Line AD = 3 units on polygon ABCD while line PS = 4.5 units on polygon PQRS. We can see that 3 * 1.5 = 4.5. It means that 1.5AB = PS
Again,
Line BC = 4 units on polygon ABCD while line PS = 6 units on polygon PQRS. We can see that 4 * 1.5 = 6. It means that 1.5BC = QR
Therefore, the scale factor is 1.5
Polygon PQRS is an enlargement of polygon ABCD