This is just a little basic helper tool to make using the /clone command a little easier. Normally when using /clone the final (target block) coordinate is supposed to represent the lowest, northwest point in your bounding selection. This is a huge pain in the ass because it means you have to turn on F3 debug coords then figure out which one of 4 possible corners is the most NorthWesterly. Even if doing that is not too hard, that corner may not be the most convenient corner for relocating your clone area.
That's where this helper tool comes in. Using this tool you can specify any two opposing corners to clone as normal, but the target coordinate is simply where you want the start corner of your area to end up, no matter which of the 8 possible corners the start was defined as. The tool simply works out the correct offsets and shows the resulting /clone command you would need to run to achieve the desired clone position.