As you suspect, the second image has a circle "cut out." To "cut out" means "to remove a piece from inside of something using cutting." The grammatical object of the verb "cut out" is the piece that is removed.
The first one has the end "cut off" (which means "to remove a piece from an end or an edge of something using cutting"). So it seems to me that by elimination, the last one must be meant to represent "cut." The grammatical object of the verb "cut off" is the piece that is removed.
Unfortunately, Macmillan dictionary doesn't seem to provide a complete definition of "cut" here: http://www.macmillandictionary.com/dictionary/british/cut_1
The most relevant definition I can see is 3:
[TRANSITIVE] to injure a part of your body with something sharp that
cuts the skin
In fact, "cut" can also be used to refer to a knife, pair of scissors or other sharp tool making a mark on anything (such as the rectangle in the figure), not just a part of the body, without separating it into more than two pieces. This distinguishes it from "cut off," which always implies separation (it's much less serious if I "cut my finger" than if I "cut off my finger"). The grammatical object of the verb in this sense is not a piece, but the entire original thing.
It's not just limited to body parts: if you do a Google search for "cut a piece of paper" you get images like the following:
Therefore, we can say that the third figure is of a rectangle that has been cut. It's not a very good image, but the artist seems to be trying to depict the result of taking a pair of scissors and closing them partway around the rectangle.