H61M/U3S3 Max Mem?

[Hoaty]

I just got this board. I am putting 8GB into it. 2 x 4GB Kingston. Just curious with 2 memory slots, and the board being able to support 16GB, how could you get it that high with only 4GB sticks available. Looking at the supported memory below.

ASRock > Products > H61M/U3S3 > Memory Support List

Again, the 8GB is fine. Maybe someday down the line when the next greatest game comes out might look for more.
thanks in advance.