To get 16gb, use 4 * 4gb modules. Each module used 2GB technology.
Just purchase two 4gb modules, you will be in spec. And, memory is cheap.
It refers to the density of the memory, typically meaning chips on both sides of the module.
Do not get hung up on this, or insisting on using one 8gb module. Just use 2 4GB modules and you will be fine (and in spec).
The board can only support 1Gb and 2Gb memory technology (this is the technology of the chips used on the DIMMs). This means that the maximum supported DIMM size is 4GB. 4 x 4GB = 16GB total. That's it. If you don't like this limit, don't purchase this board.
Please read the following documents. This is what is supported as far as memory and processors.
If you want to play with something else, then that is certainly your prerogative . Just do not complain when it does not work or you cannot return it or you damage your board,.