The Autodesk Wikihelp says that this is for graphic display only yet the Type Properties dialog offers a value to change using a structural unit instead of integer or number data type. It does affect the height of the annotation as suggested by help but the value you enter seems a little odd?
...snip Force Scale The display size parameter; this value visually changes the display of the force symbol. Scale is for display only....snip
Same thing for Moment Scale.