For most doors a complete rotation of the screw allows the door to advance 2 inches.
Garage door only goes down a few inches.
The garage door can be operated manually by disconnecting the garage door opener from the door using the red pull cord.
My garage door opens about six inches and stops i press the button twice so it will stop going down and then is goes up another 6 inches or so.
It goes partway down reverses direction and goes back up again.
This just started a couple weeks ago.
Try to lower the door.
You push the button to close the garage door.
My garage door will open only a few inches and then stops.
Turn the down adjustment one full turn counterclockwise.
Clicking the remote at that point just closes it.
If the door is working properly it should be easy to lift by hand.