One of the most important safety features of your garage door is the force setting. It regulates the amount of power needed to close and open the door. There is also a down and up limit. This safety feature can also detect if there is some obstruction in the way. If you have to set the limits higher than the normal setting, there is most likely a problem with your garage door.
You can test the down limit setting of your garage door. Just simply place a 2x4 wood block on the ground. It should be placed beneath the bottom of the garage door. Ideally, the door would reverse if it comes in contact with the object.
If you think that your opener is not correctly adjusted, you can call your local garage door repair professional to assess the problem and resolve it.