So, a translate of 72 moves 1 inch. Otherwise, you have to multiply by the scale factor to get the true translation. Kind of a pain. Moreover, it is unclear where the origin of the coordinate system is, and it is also unclear to which part of the postscript image the coordinates are anchored. Your best bet is to just guess what the factors should be, check it out with gs or ghostview and iterate the solution.
Scale makes much more sense.
The x and y factors are simply the magnification in each direction, normalized so that 1 is just the original size. Where angle is a number in degrees, that specifies the amount of rotation, measured counter-clockwise from the original orientation. That's all I know.