There are a ton of good threads with more of this information.
I get kind of lost when I start chasing these things around sometime.
I was looking at one thread where a car was lifted on a driveway that looked like pavers but may have been stamped concrete. The jackstands are all correct but using a floor jack on an uneven surface may "pull" the car as it is lifted as the wheels of the jack won't roll.
The owner of this car may have placed the jack on plywood or something to prevent this from happening.
Is this correctly jacked on axle stands ?
Have a quick look through some of the old threads, the info will keep you honest while doing a lift...