No option to turn off size display of screenshooted region
Upon updating to xfce4-screenshooter version 1.9.9, a small feature has been added apparently. Next to selection crosshair, in bottom right corner there's shown size of screenshot being taken. Dragging selection from top left to bottom down makes size indicator to be positioned outside of shooted region.
On the other hand, dragging from bottom to top or right to left makes this overlay a part of screenshot to point where taking small enough screenshots actual content is obscured by indicator