How to keep featured image the way it looks on post in home page?

I’m trying to make the featured image on my most recent post look the same on my home page as it does in the page for the post itself. It looks right for the post below that, but on the top post the picture is shrunk and to the left, not full size and centered.

I tried using the Simple Image Sizes plugin, but I don’t know enough about how it works to solve the issue.

Thanks!

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