I think you forgot to include the image but i did some testing and the plugin does specify that the image needs to have the size that you defined, this is very technical but in case it helps, this is the code that the plugin generate for the email (which specify the with that i defined)
td style="text-align: left;">
<img src="https://test:9090/workstation/wp-content/uploads/2023/07/image.jpg" style="width:56px;"><div class="par" style="margin-bottom: 5px;">
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Also the image looks fine in the email provider that i am testing with. So it could be that your email provider is just ignoring that setting and display the image in the original size. To fix this the best solution probably is to resize the original image with a tool like https://imageresizer.com/ and then use that image instead. That way even if the email provider render the image at the original size it will still look fine.
Regards!