Negative numbers

1

I am trying to work this out


	obj.pram2=-86.2;
	var adjustMask = -170.2-obj.pram2;
trace("adjustMask  :"+adjustMask );
output=adjustMask  :-84

When I do the Math on a calculator it works out to be -256.4 which is what it should be. Why is this happening.
-170.2 subtract -86.2=negative 256.4