What size should a cover image of a post be?

Smitter - Jul 31 '22 - - Dev Community

What size should a cover image of my dev.to post be? When I hover over the add cover image button, I am advised to use 1000:42 ratio image for best results. As illustrated in the image:

Create post screenshot
When I resize my image to be 1000px width and 42px height, I get undesired results. When I don't resize, the main areas of my image shift out of focal view.
Am I converting the ratios incorrectly?
If yes, then what is the right way?

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