Once they move, they stay there. They don't snap back. That's characteristic of a synthetic nylon type of string. The difference is, if it's tight enough it won't move in the first place. If you have an iPhone, you should download RacquetTune. The string factor for PPA is so close to the default value that you can just use the defaults and your reading will be accurate. Your strings seem to be moving with very little effort from you. I would bet that if you measure it with RacquetTune, it will be in the 40's.