Hi there,
GP uses the unsemantic grid system: http://unsemantic.com/
So we only have the percentages they offer.
That being said, there would be waaay too many options if we went far enough to include the percentage by 1% or 0.1%.
Of course, you can alter the CSS to be anything you like.
Say you have it set to 25%, your HTML would be:
grid-25 for the sidebar
grid-75 for the content
Which = 100%.
So you can alter that CSS like this:
.grid-25 {
width: 25%; /* Change to whatever percentage you like */
}
.grid-75 {
width: 75%; /* Just make sure the two of them equals 100 */
}