I searched and found a matrix that says the OptiPlex 7040 Small Form Factor can support up to 64GB of 2133 Mhz DDR4 memory. But I  don't see anywhere where it says what configurations it can be in?

Right now I have 8 GB, and I believe it is 2x4GB modules. I want to get more memory. If I get 2x8GB modules can I simply put those in with the 2 4's that are there already?