This menu command starts the Trimming.
If you choose Proportional to Paper Size trim type then the aspect ratio of the displayed cut is identical to the aspect ratio of the currently selected paper size (see the Paper Size dialog), regardless of the aspect ratio of the selected cut. To ensure such proportional aspect ratio of the displayed cut, the size of the displayed cut area is usually larger than the size of the selected cut area. Note that if the Dynamically Trim item in the Options menu is checked, the trim type (Exact or Proportional to Paper Size) is determined by the Prefer Exact Trimmenu item switch.
If the Proportional Aspect Ratio item in the Options menu is not checked, the selected cut area is always identical to the displayed cut area (conforms to Exact trim type) and is fitted to the entire drawing area. This usually leads to the deformation of the displayed image.
To expand the picture into the original size press the Tab key or use the Expand menu command or press the right mouse button followed by pressing of the left mouse button (while still holding the right mouse button) or press the middle mouse button if you have any.