Help with margins format of EPUB books to Kindle app

[alibi272]

Hello!
I apologize if this is the wrong place for this post, I'm very new to this!
I am trying to take EPUB files I have in Calibre and put them into my kindle app for my iPhone and iPad pro. When I load the book in my phone it looks great, the margins are correct and the format looks awesome. When I read them in my iPad the margins are obviously much too small so the book does not fill up the screen fully. I have tried changing the output to iPad in calibre and changing the page margins but nothing has worked. I think it's because my screen resolution is much larger than the one for the iPad but I don't see any options when I look for a bigger screen.
Does anyone have any ideas on why this is happening?