In the picture below, the sizes set on the pop-up dialog were width = 20 mm and height = 5 mm for both the hinges drawn.
This is the repeat shape. The hinges drawn above have a horizontal repeat of 2 shapes and vertical repeat of 7 shapes.
To get the hinge drawn with exact sizes you must allow for the spacing between the shapes.
The second hinge in the picture has the same size settings but the whole hinge has been scaled to fit in the drawn rectangle. This means that the width and height of the repeat shape have been adjusted.
The width is now 17.5 and the height 5.3.