Yeah, I gotcha! Rarity is basically measured on a percentage that denotes how likely it is to be found. So, something that has a 15% rarity, for example, would mean it's pretty rare because it reads like a 15% chance to be found. A 95% rarity item would be common.

At least, that's how I try to remember it. That might not have been the intention! The lower the number, the rarer the item!