For adding you will get result in second parameter (Y in your case), and for multiplication in first parameter (X in your case).
Ex. X = 2 and Y = 10
ADD X TO Y. "this will OVERIDE the value of Y with result. (X = 2 & Y = 12)
MULTIPLY X BY Y. "this will OVERIDE the value of X with result. (X = 20 & Y = 10)
Hope this helps.
