Actually I believe that to be incorrect.
The manual memory installation instructions are on page 16 and are written in a manner that could well be misleading.
It mentions the Channels being 1 and 3 with 2 and 4 being the other however the chart shows no such placement.
Additionally it clearly states that to enable dual channel mode you must use the same color sockets which the picture of that board shows as being the first two sockets or the second two sockets.
The sockets are color coded for a reason so if instructions come off as iffy then there's always that to fall back on.
Yeah, I am wrong. I just realized that AMD MB from Gigabyte use different configuration as Intel ones after reading the manual just downloaded.