The ResetObjAnnoScales command will add the current Annotation Scale to the scale lists of the selected objects (if necessary), while simultaneously removing all other Annotation Scales, leaving only the current Annotation Scale in the list.
Type ResetObjAnnoScales at the command line and select items on the screen. Right-click or hit ENTER when you are done.
This command is basically a short-cut for editing the Annotative Scale List. It does the same thing as manually editing the Scale List associated with the selected objects.