Using Corkian Amplifier

Hi,
I'm wondering how this works:
I have a lvl. 85 chestplate.
It was 69% (using the wynntils mod)
After using the corkian amplifier with the item identifier, first time went wrong (I clicked the wrong mouse button :) ), because of this it went to something in the 40%
Second time I clicked the right button, so it went to 56%
I wanted to use a corkian amplifier again (for a hight cost) and now my chestplate is back to 49%
How does this work?

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I tried it on a different item, and using the corkian amplifier made the item worse again

 

rerolling an item, regardless of whether you use an amplifier, will completely randomize all its stats. the current state of the item is completely irrelevant

amplifiers will slightly skew these stats to be better, but there is no guarantee that it will improve your item