I searched these forums and found someone with a similar question and one of the answers came from The Architect himself, so I shouldn't try to explain it myself.
But I will anyway. KM gives you the tools to place the windows anywhere you want on either screen using a single coordinate system that combines both monitors in a single coordinate system. It's up to you to be aware of the coordinates for both screens. But if you move the screens around using System preferences, the coordinates will change and you have to handle all that. Are you prepared to handle all that?
On this web page it appears to me that someone tried to solve the problem using screen numbers, as it appears that you want to do. The comments were that the macro worked well. So try it out.