Denniss, you're right. I had to double check that, we use another letter for byte in the Finnish abbreviation.
The question is, do the writers of the manual know the difference, or care about it? Logically thinking, if the mobo has six slots and a maximum of 24 GB, it would be 6 x 4 GB. Then again, half of the slots are of a different colour so 3 x 8 GB would result the max as well in triple channel mode.
Dyna, since you're getting a 4 x 4 GB set, I suppose you should be able to leave a 2 x 2 GB set for a total of 20 GB. What I don't know is, should you put the smaller modules to slots 1 and 2 or 5 and 6. In the former case, if the motherboard fills the sticks with data in arithmetic order, the small sticks and the second pair might be full all of the time and the third being partially used which should not make a gap caused by jumping from one pair to another for added space. In the latter case they'd be idle most of the time which may or may not cause a minuscule delay every time they'd be used. Most likely I'm just exaggerating the issue.