If you get the chance to use this machine, definitely try it out! Assisted pull up machines are fantastic for building up strength to progress on to full body weight pull ups and chin ups.
The only thing that can seem confusing at first, is the weight settings.
With other weight machines, the settings are very straightforward. If you want to lift 50 pounds, you place the key in between the weight plates that say 50lbs, or the number 5 or five plates down. Easy breezy, right?
However with the assisted machines putting the weight at 50, actually means 50 pounds assisted. So basically it's giving you 50 pounds help while you are using your weight for the rest of the work. So if you are using 50 pounds assisted and you weight 150lbs, you are lifting 100 pounds of your own body weight.
If you want a good estimate of how much assisted weight you need, go to the lat pull down machine and see how much weight you can do 10 reps with. If you can lift 50 pounds and you weigh 150, then you need 100 pounds of assisted weight on the assisted machine.