Why? Because they are mirrors of each other. In other words, one table has its x and y row swapped compared to the other table.
The input x = -120 leads to the output y = 627 in table C. Then in table D, we have the input x = 627 to go the output y = -120. Refer to the first column of each table mentioned. The same applies for the other columns as well. The inverse table undoes everything the original table does.
