Summarize:

To get many of the measurements, particularly dept, you will need to move the refrigerator. When doing so, be sure to remove everything in the refrigerator and have at least one strong person on hand to assist you. Do not leave any shelves in the refrigerator that can be jostled during the moving process. Either take the shelves out and move them separately or use tape to secure them in place. Be sure that the doors don't open up while you move the refrigerator. Either take a strap and tie it around the doors or wrap tape around them. When moving a refrigerator, don't ever lay it on its side. Place the measuring tape against the back of the available space. Extend the tape out to the front of the counter. Write down the number on the measuring tape. Not only is it possible that you misread the tape measure, it is also possible that your house has settled. In the process, some of the surfaces might become uneven. Repeat the measurement at a different point in the space allotted for the refrigerator. If there is a discrepancy, use the smaller measurement. It is better to have too much space, not enough. If you have not allotted two additional inches on the side for the door hinges, you will need to move the refrigerator two inches out from the counter space to give the doors room to open. This will allow you more room for depth, but you will need to verify that the doors do not extend too far out into the room. Refrigerators require ventilation to work properly. There must be at least an inch of space remaining behind the refrigerator.
Move the refrigerator. Measure from the back of the space to the front of the counter. Repeat the measurement. Decide if you want the refrigerator to extend past the counters. Allow at least an inch of space behind the refrigerator.