If the stock is true to what it claims, and is working correctly, you should be able to place and lock the stock in six different positions.
Fully opened (pulled all the way out) is one
Fully closed (pushed all the way in) in another
There should be 4 intermediate lengths in between that can be locked into place.
Basically there should be six different lengths you can set the stock to.
If that is not the case, then either the stock is working incorrectly or you have a mislabeled product.