Short version: Consumables saying +10 Experience instead of +10% Experience.
As a new player I always thought food/consumables gave +10 Experience from kills, which I thought was extremely small later on, only to find out it actually means +10%.. at least according to online sources. I took a second look when I found +15% on 1 consumable and made me wonder if the +10 was actually to mean +10%…