I noticed this as soon as I added an Adata Dimm to my Motherboard.
It started to show the Dimm as slot 2(or 1 based on Softwares that start from 0 or 1).
Before this I have used CPU-z and HWinfo and when I had 2 Dimms it showed it as 0 and 1.
Now I see this. I even tried switching the slots...
