Im asking because I want to use the armor and jewelry enchants for defense and majick.
Well, bear in mind that the "percentage" is your chance of success, and it's capped at less than 100%, meaning there's always a chance of failure. So, when you're testing various things for effectiveness, you need to test more than once, to get an idea of success rate.
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Your percentile will never show up as being over 90% chance of success (at least in my experience). the advantage with potions truly comes when the object of your endeavor is very expensive and heavy. If you check success chances (shown on the right under the object) you can see that an item like a enchanted gold diamond necklace has a 35% chance. If you stop and take a potion that adds 25% chance, your odds will then go up to 60%, but never over 90%.