I'm wondering if someone could give me some advice on what size to make an image or how to properly size an image when creating a calendar event. I've created three different events over the past few months and each time the 'poster' or image I've used in the event comes out too magnified. I've tried sizing down the image each time and renaming and re-uploading the image but it stays the same magnified state. I would love to know what I'm doing wrong.

Thank you for any help!