You may decide if you what to display your image to actual pixel width or a percentage width of the frame.
Width (%) is a critically important tool for responsive design as it allows you to determine the width of the image in relation to the frame. In considering how the image will render on all devices MOBLE CMS automatically sets your image to 100%. This will ensure that your image will stretch to be 100% of the frame irrespective of the size of the device. I.e. it will automatically shrink and expand to fit the device through which it is being viewed. If you wish to reduce the size of the image, consider reducing the percentage of the image width, rather than reducing the pixel width.
Width (px) will set the image to a fixed pixel width. If the device screen is smaller than the width of the image, then the image will overflow to the right of the screen.