It's not play, it's the spring being completely unloaded with the car in the air and you being able to load them a bit by yourself. I could fairly easily move both sides of mine up a couple of inches when it was jacked up. As to why the amount is different from side to side, I don't know but unless you are aware of a real problem when driving I wouldn't worry about it. If there is a problem, the first place I would look would be one or the other shock absorber. You could try swapping them from side to side to see if anything changes.