The details are right below the chart. all 5 of those specifications are critical to compatible RAM. Unbuffered\Non-Parity is the difference between consumer devices versus high end servers (not interchangeable). 204 pin is the slot specifications, anything else won't fit in the slots. PC3-14900\1867MHz DDR3 is the type and speed on the RAM.
Although the specs you show state 32GB is max, crucial (and OWC) have found 64GB is max (Apple purposely understated max memory on several models over the years). But, the question is, do you really need that much. Memory will speed things up to a point, but SSD will have a greater impact for most users. If you do high end video\audio editing, or work with large files, more memory may help. But, there is a point at which more memory is just a waste of money. For most users 8-16GB is more than enough.
Since you have 2 4GB (8GB) now, and there are 4 slots, you should be able to add two more sticks of 4GB to get to a 16GB configuration. You could also add 2 8GB sticks for a 24GB total, or replace the 2x4GB and add 4x8GB for a total of 32. Memory is installed in 2 banks of 2 slots on your model. Generally, it is ok to mix capacity so long as each bank is populated with equal sized and spec memory. Apple doesn't address mixing memory in their guides, but in most Intel PC, the memory must match in the respective banks. So, note the slots the factory installed RAM are in, this is bank 1 (not likely to be adjacent slots). So, if you mix memory, add the new sticks in the two empty slots.
A video on replacing RAM on your model:
The official Apple guide for you model is here:
http://help.apple.com/imac/late-2016/#/apdd768f6349