Not sure I understand the question. To retract them (ie, put them back into the outer leg as far as they go), you press the leg button and then push the leg in, and then release the leg button. You cannot pull the legs out without pressing the leg button, and when you do, it's not like you can actually pull it because it wants to shoot out.
When you press the leg button, the leg will push itself out until it is stopped by something or it goes all the way out. The intended way to operate this efficiently is to cant the rifle slightly with your firing hand (eg, turn rifle clockwise if you need the left leg a little longer) while with your other hand, pressing the leg button. The leg will extend to take up the slack and you then release the leg button. Repeat opposite direction for other leg. Same exact biomechanics as the AI/PH bipod.
To shorten the leg, you do that but don't tension the rifle with your firing hand, and the weight of the rifle will be enough to slowly-ish push the leg back in until you release the leg button.