Object oA is repositioned relative to it's current co-ordinates. It's new co-ordinates are X+vDX,Y+vDY where X,Y is it's current position. If vDX or vDY are greater than 127, they are treated as a negative number (vDX-256 or vDY-256).
v254 = 5;
v255 = 252;
would reposition object 1 to X+5,Y-4.