I am not really sure that I understood your question.
If your question was if that you can have RAM-pieces with different capacities in different sockets then there should not be a problem. I don't think that the amount of RAM needs to be evenly divided between the sockets. Just make sure that the new piece of ram shares the same DDR-value as your previous ones and that your wearing a groundingbracelet.
I recently made an upgrade of RAM to my pc, I had 8 GB of RAM before and I added 2x 2GB in the two other RAM-sockets that I had, and it works perfectly fine. As I said before though, just make sure that the new piece of RAM share the same DDR-value as you existing ones.
Cheers!