Answer:
Suppose that you have a random point (x, y), and now you do a dilation from the origin with a scale factor of k.
Then the new coordinates of the point are:
(k*x, k*y)
Now, in this question, we have a dilation of scale factor k = 1/2.
Then if we start with the point (x, y), after the dilation we will have the point (x/2, y/2)
Now you can notice that instead of this, in the table we have (2*x, 2*y)
So this is the error, the transformation is not correctly calculated.