change wordpress email format

Hello, I am using a ecoomerce plugin which sends new orders via email to my eprinter. All mails are printed with lot of space around the “main” box. I attached a screenshot that u can see. I asked the plugin dev (restropress). He said I need to change it in the wordpress theme, but I have no idea how or where. Does anyone have an idea?

This is how it looks: https://ibb.co/hcjnRXJ
This is how I need it: https://ibb.co/x66vgmN

Thanks for your help

The page I need help with: [log in to see the link]