Thunderlords decree is supposed to have .1 ap scaling, but has .2 in game

^ Title. I noticed in my normal game as katarina that my thunderlord's ap scaling was double that of my ludens(should be the same according to the in-client tooltip), then tested it in customs to confirm. It definitely has a .2 AP scaling. I'm not sure if this is a visual bug and it actually has a .1 scaling, or maybe the tooltip is mis-worded and it's supposed to have a .2 scaling ( I sure hope so xD) or if its just legitimately bugged.