(Names changed in Phatch 0.2)
A use case is described in this tutorial.
The depth of the reflection which can never be larger than the height of the image.
The gap between the image and the reflection
If the depth is smaller than the image height, you could scale the reflected image so that it fits totally in the reflection.
Only if Scale is set to true, this describes how the reflected image should be scaled.
Put this on zero for transparent images (png, …) or on 100 if you don't want any transparency.