I thought that's what you meant. Okay say you have a Pokémon named B and you are fighting a Pokémon named Z. B has 100 Defense and 100 Special Defense. Z has 200 Defense and 200 Special Defense and Z has +2 Special Defense and +2 Defense. B uses Guard Split. Now both Pokémon have 150 Defense, 150 Special Defense, +1 Defense, and +1 Special Defense. If you then switch B out, B will revert back to 100 Defense and 100 Special Defense and +-0 Defense and +-0 Special Defense, but Z will keep the 150 Defense, 150 Special Defense, +1 Defense, and +1 Special Defense until it switches out.
I hope that made sense XP