Rhia, we have that discussed deeply in that other threed. The DPI is only the crosslink between digital size (defined in pixel x pixel) and the printing size (defined in inch x inch or cm x cm as you are used)). So VedaDalsette's way is absolute correct. Define your render in pixels for height and width as you want to see and give poser the size for your print as inch by inch and you will get a optimal output. Or a other way define your wanted pixel size for rendering and give the cross calculating value as DPI. In this way Poser should estimate the print size (or viceversa the render size with given print size) itself and indeed this way seem to be trashy in Poser 12. But no real problem cause you every time can get the correct output as you wish.

And truely no need to open up that other threed again cause there was all and more said and even given a lot links to interesting and true internet links from printing and/or photography where this absolute super easy theme is also known.