Yes Martin is right (is that a pleonasm?).
Beware of adjusting something while misaligning something else into the bargain!
If you touch arm parallelism, it can influence the aperture setting too.
When you pause/play the arm should lower and the carriage must not move at all. If it does, it is not properly aligned. This can be tricky to do and if you don't feel you can do it, then don't. If you feel up to the task, do exactly as per manual's instructions.
For what it's worth!