From Dark and Darker Wiki
One thing I can't seem to find any mention of here is that some stats are mutually exclusive. I see the "Enchantment Exclusive" section as well as the "additional restrictions on enchantments" mentioned near the top.
However, one thing that is missing from either of those sections:
Some stats are mutually exclusive and cannot be combined or rolled together on a piece of gear.
A great example of this is True Physical Damage and Additional Physical Damage.
Another example would be both True Physical Damage and True Magical Damage.
Don't believe me? Try finding those items on the marketplace. They do not exist.
Jewelry/Gloves can roll True Physical Damage or Additional Physical Damage, but not both.
The reason this is important is because, as I'm attempting to calculate my odds of getting, say, True Phys Damage and Phys Power on a ring would be calculated differently than this wiki implies given this piece of information.
It cannot be calculated by "Math for 'At Least One in N trials'", since your probability for the second attribute changes once you have the first attribute selected.
We also don't know that these probabilities are divided evenly. Perhaps one attribute has a higher chance of spawning on a particular item compared to another roll/item.