Potency is the level of the rune. Each level has an additive and a subtractive type. The levels overlap, so 1-10, 5 - 15, 10 - 20 etc. You have to have the correct level potency for the item you want to equip it, but you also need to have the right type (additive and subtractive).
I would recommend using this site. It helped me a lot. http://elderscrollsonline.wiki.fextralife.com/Enchanting
turbonights wrote: »Aspect - How much of (your normal color tier)
Essence - What stats
Potency - What level/strength
A level 8 potency will not be as strong as a level 9. There are multiple types of potency for armor/weapon glyphs. Once you "decode" or do your first enchant, you will always be able to see what the combinations can enchant to.
Example: Level 8 potency additive is "Recura" and when decoded called Magnify
Level 9 additive potency Cura and is called "Intensify" when decoded.
Intensify is stronger, but can only be applied to VR10-14, where Magnify can be applied to VR7-9.
freespirit wrote: »Potency Runes basically set the Glyphs level ie the level of gear you can put that glyph on.....
They come in two forms increase and lessen but different words are used on most of them such as 'exaggerate' and 'deprive'