You are not doing it wrong. But the move in percent (the two fields below the unchecked “Use Default Offsets”) is relative to the size of the shape and has nothing to do with the size of the bounding box of the text (which you can adjust with the two fields just below). In your second example, the center line of the text is just the horizontal size of the shape to the right (=100%) of the center line of the shape. In your third example, the left side of the text is just the horizontal size of the shape to the right (=100%) of the left side of the shape.
So the move in percent maxes out at 100%? Is there a way to move the text further to the right?
I can alway delete the text completely, create a new text box in the appropriate position, and group the new text box with the shape. It just seems to cleaner to use the shape’s original text box.