MSI KT4V (KT400) Memory slots question

I don't see the mobo on the MSI site, but there are 3 memory slots. One is a little off the side to the others, and the other two are kind of group[ed right next to each other. What does this mean, and what order should I put them in? It's like this.

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I have my sticks in slots 1 and 2 right now, should I change it? I didn't see anything about this in the manual....