screensaver not filling screen

Running the OSX version of the app to make Win screensaver. (Great feature!)
Everything seems to work OK except that the screensaver on the PC does not fill the screen. There is black at sides & top/bottom. As in attached image.
I see the same thing on two different PC.
thanks in advance

Hi Scott, glad you liike the product.
iScreensaver allows a range of sizes and motion. Some of the options will fill the screen, and some will not.

Because screens come in different aspect ratios (width to height ratio) it’s generally not possible for one screensaver to perfectly fill the screen on every computer. So you either have to choose to have black bars on the side or top/bottom (this is called “letterboxing” ) or you can have the image expand to fill the screen completely, with some edges perhaps offscreen (this is called “crop” mode).

See for details.