How Do I Adjust Default Settings for Shadows (or Other Object Attributes)

After I insert an image (File–>Place Image), I select it and apply a shadow. I apply the shadow in the Object toolbox, in the Shadow subsection, by selecting “Immediately Below” from the shadow drop-down menu.

When I do this, the image immediately has a shadow of “0 in” right and “.02778 in” down.

How did those default numbers get set? And can I adjust them? I create thousands of screenshots. Removing just a few clicks is worth a bit of bother.

(Note: I add shadows to screenshots, along with callouts/circles/etc in order to edit screenshots that have white backgrounds so they can stand out against white backgrounds when they are placed in documentation.)