The IF statement below checks to see if we have landed on a target and if we have and it's not covered then we set the objects X Y coordinates equal to the X Y coordinates of the target using the arrays we build. We also set the cover of that target to 1 or TRUE so you can't drop anything else on that target.
If either the target is covered or we aren't over a target then we used the variable that we set upon release (my_num) and we set the object back to its original X and Y coordinates.