Reflection capture "pivot" movement (small sprite)

In some scenes I’ve seen that the Box Reflection Capture has the small sprite moved out of the center of big sprite (i.e. position) so that you can cover the whole room but have the reflection capture occur at some different point inside its bounds (for example closer to the light source). Thing is I have no idea how to move that pivot/small sprite and I’ve been unable to google anything useful. any ideas?

Just found out that there is the Capture Offset hidden in “advanced” options.