Enabling resize: check the Enable Resize checkbox to turn on the resizing option. When Enable Resize is switched off, all the images retain their original sizes.
Interpretation of Width, Height and Percents controls values depends on currently selected resize mode.
Fit Width mode - image will be resized to match specified width. It's height is not significant.
Fit Height mode - image will be resized to match specified height. It's width is not significant.
Exact Size mode - image will be resized to match both height and width specified. Image aspect ratio can be changed during resize.
Percents mode - image will be resized to the specified percentage from original size.
Auto Crop mode - image will be resized to match the specified size. Image cab be cropped horizontally or vertically.
Crop Width mode - image will be resized to the specified height. Image can be cropped horizontally if it's width after resize exceeds specified value.
Crop Height mode - image will be resized to the specified width. Image can be cropped verticaly if it's height after resize exceeds specified value.
The Sharpen option is useful when you creating small thumbnails. Turn it on to produce more sharp and clear thumbnails.
When resize option is enabled original image will be resized according to specified size and mode. But final image size can differ from the specified one. More exactly, Frame and Shadow features increase image size. See Result Size inscription under preview window to find out exact resulting size.