“Attribute image.width has an invalid value”

I am getting an error on Google’s structured data testing tool pertaining to my post’s featured image:

“image”:{“@type”:”ImageObject”,”url”:”http:\/\/www.mywebsite.com\/wp-content\/uploads\/2016\/07\/image1.png”,”width”:300,”height”:159}}</script>

Is there a setting I need to change in the post itself? In the source image file?

Or is this plugin’s markup language incorrect/missing quotes? I found another post that said the thing should read

“{“height”:100,”width”:100} should be {“height”:”100″,”width”:”100″}.”

How do I get those quotes added?

Thank you very much,

KG