You are not interpreting the instructions correctly, at all. hScale and vScale are NOT the dimensions of the display, nor should the values be enclosed in braces.
By default, you shouldn't have to do any of this unless you want to make the entire UI larger or smaller on your display... nUI will automatically scale itself to fit any and all display resolutions that WoW supports without any editing on your part. To accomplish that, remove the scale, hScale and vScale entries from your nUI options section and you're all set.
Now, if you're trying to alter the scale of the entire UI for your particular display, then you should start with the following...
Code:
nUI_Options = {
["scale"] = 1,
["hScale"] = 0.75,
["vScale"] = 0.64125,
}
Now, to make the UI wider, make hScale bigger, to make it narrower, make hScale smaller. Likewise, to make the UI taller, make vScale bigger, to make it shorter, make vScale smaller.