The idea is to allow you make a large render when your UI has only a modestly sized document (preview) window. For example, you're working on a laptop, and only have UI space for a 1024x640 document window, but you want to render at 1920x1200 pixels.

Poser 12, in feet.  

OSes:  Win7Prox64, Win7Ultx64

Silo Pro 2.5.6 64bit, Vue Infinite 2014.7, Genetica 4.0 Studio, UV Mapper Pro, UV Layout Pro, PhotoImpact X3, GIF Animator 5