When you create multi-column emails you want to align your columns' content. So you would often want to make image size the same as your text content (in most cases you need height).
Now you need to use browser's inspection tools to get the left column height. It would make life easier if next to the "Container" controller you just add its size – either both or only height would be enough. Just like this: Container (H: 321px).
It will help to decide how to crop your image before placing it to your email