Enchants and Masterworks taking incorrect durability

A guild mate of mine created some obsidian plate gloves for me. The enchant and masterwork durability reductions are not adding up correctly. I am not sure if this would be repeatable as it would be expensive to get more obsidian chips and try to get the exact same three masterworks and enchants again. Picture is attached below showing 1 enchant taking -10, and 2 masterworks taking -5 each. This should total up to -20, but -25 is taken from the total durability of 50. These are unused, straight from the forge to enchant table.

Reproduction rate: ??? expensive to attempt reproduction

Steps to reproduce:
1. Craft something
2. Enchant and/or masterwork the something
3. Get incorrect durability calculation

User specs: PC running Windows 10 64 bit, game version 64.554

 

I decided to do a little more research. This seems to be mostly effecting gloves and boots. I visited one vendor and found at least 10 items that were affected by an incorrect durability calculation. Attached is a screen shot of 6 items.