Welcome to the Shopify community!
Thanks for your good question.
It's issue occur Due to your product image size.
Please share your site URL,
I will check out the issue and provide you a solution here.
I don't want to change my product image for that cushion in my screen shot...
I want the orientation to be rectangle in the product page for that specific product.
Is there any solution to JUST change the size on the checkout??
checkout page customization allow only for Shopify plus plan
thanks bt your store password protect