I'm new to CK2 and I get confused a lot.
I started as Earl of Ulster, and before my initial Earl died, I changed succession law to 'elective'. I made my daughter elected (barely - some mayor almost got elected instead). A bit later she was able to claim the title of Duchess of Ulster.
But then I notice that my succession law is Gavelkind. I said to myself 'This is probably how it works', and continued playing. But then I noticed popups about who supports who continue to happen! And they talk about County of Ulster, not Duchy:
Is this a bug? Or am I missing something here?