When you work with images there are some settings. For amazon they are:

- preferrable image size,

- image size in template.

Preferrable image size parameter uses on search ( you need redo search after change this parameter ). When you change this parameter Amazon will return new image size for you that you can use in your post.

But you can also change returned image size by using Amazon template. By default image size is 100%, so when you use default template image can be on all your post ( 100% ). 

In this case you can use another template, or of course change image's width. ( You need to redo your search after that ).

In case of 13% width we have much more elegant post: