To change the Swf Display size:
a: move the slider to enlarge or decrease the Swf Display size
Note 1: through this parameter all the elements in your slideshow will be increased or reduced.
Note 2: To modify all or some slideshow components click on: "Modify Template" to launch A2 Flash COMPOSER (if present)

Box "Full-Screen":
it shows your slide-show in full-screen size
a: Check the box to set this option

To verify the changes:
a: Click on: "Preview"
Note: to speed up the action the preview show only some uploaded images

More info: Please read the User Guide