Resizing Grouped Objects
Many of the symbols in the software libraries are
grouped SmartDraw objects. These SmartDraw objects
grow and shrink together as if they were one shape.
Due to restrictions on text shrinking, some grouped
objects will be distorted when shrunk.
To change the restrictions on text shrinking, select the shape, go to the Design tab, and select Text Entry Properties from the Shape Properties group.
Check the box under Allow Text to Shrink and specify a small size such as "8". Now, you should be able to shrink your object without distortion.

If you want even more freedom in editing these symbols, you can ungroup them in the Design tab under the Shape Layout group's Group command.
Once ungrouped, you can stretch, shrink, and grow the elements of a symbol separately and reassemble them to your liking.