Where grade permits

I was told that my unit has a door to garage. However, the document says "Including: Door to Garage (where grade permits)". If there is not this door, I have to get out of the garage and go entrance to enter the house. Even my unit has door, but I didn't understand the meaning of "where grade permits". I asked Ms. P and she gave me the answer. If only the garage is in the undergrand or semibasement or something, the level is not equal to the house. Then it is impossible to install the door. Grade means slope in this case. The garage in my unit is on the ground floor, there is no ploblem to install the door. What a relief.